A hybridized electromagnetic-triboelectric nanogenerator is to utilize electromagnetic and triboelectric nanogenerators to simultaneously scavenge mechanical energy from one mechanical motion. As compared with the individual energy harvesting unit, the hybridized nanogenerator has much larger output power, higher conversion efficiency so that it can be used to solve the power source issue of some devices with larger power consumption. The hybridized nanogenerators have the potential applications in self-powered sensors, wearable devices, and networks.
Rapid advancements in various energy harvesters impose the challenge on integrating them into one device structure with synergetic effects for full use of the available energies from our environments. We report a multi-effects coupled nanogenerator based on ferroelectric barium titanate, promoting the ability to simultaneously scavenging thermal, solar, and mechanical energies. By integration of a pyroelectric nanogenerator, a photovoltaic cell and a triboelectric-piezoelectric nanogenerator in one structure with only two electrodes, multi-effects interact with each other to alter the electric output, and a complementary power source with peak current of ~ 1.5 µA, platform voltage of ~ 6 V and peak voltage of ~ 7 V is successfully achieved. Compared with traditional hybridized nanogenerators with stacked architectures, the one-structure-based multi-effects coupled nanogenerator is smaller, simpler and less costly, showing prospective in practical applications and represents a new trend of all-in-one multiple energy scavenging.

Beyond the rigid or flexible frame-based electronics, the development of stretchable electronics for implementing wearable/attachable electronics or electronic/ionic skin, consisting of transistor, luminescence devices, smart sensors, and energy devices received great attention. It is required to be thin, light, stretchable, and transparent to be integrated with clothes/wears or attached on or implanted into curved human body. The triboelectric nanogenerators (TENG) convert mechanical energy into electrical energy is receiving great attention as a sustainable power source for portable/stretchable electronics because of its simple structure, many materials options, low cost/easy fabrication, and superior power output performance. In this presentation, we introduce polymer gel based stretchable, transparent, and high performance TENG that can harvest biomechanical energy and tactile sensing. We have fabricated ionic/nonionic polymer gel based dielectric layers and investigated its dielectric property, electrical conductivity, and triboelectric property. The fabricated polymer gel has improved its transparency and stretchability. Beside it exhibited an extremely improved dielectric constant and very strong triboelectric behavior that can contribute to enhanced TENG performance. In addition, we introduce a new type of tactile sensor based on charge displacement current that can sense position and pressure without electrode grid patterning.

Silicon (Si) has the maximum capacity (> 4000 mAh g-1) compares with the conventional graphite (300-350 mAh g-1), which can dramatically increase the energy density of the battery. However, due to some drawbacks on Si material such as electrochemical irreversibility and volume expansion on alloy reaction, pure Si cannot be used in large quantities in the anode electrode, approximately 3~8 wt% only in commercial products. In this research, a novel method for pure Si material has been developed, a polymer brush modified core-shell structure (PBCS) by hydrosilylation reaction on Si nanoparticles. According to the results, the PBCS structure provides three significant functions on Si particles because of the effects of hydrogen bonding such as good dispersion in the slurry, a protection during cycling, and excellent conductivity for high-rate tests. The polymer brush is fabricated by the acrylic acids in which the hydrogen bonding effects between each carbonyl groups are used to enhance lithium-ion diffusion and the adjustment of attraction and repulsion in between particles. The PBCS Si electrode shows the first columbic efficiency is 87.1%, the retentions are 92.5% (0.1C/ 0.1C) for 200 cycles and 86.2% (0.5C/ 0.5C) for 400 cycles, respectively. The TEM and TXM results display that the PBCS structure significantly protects the nano Si from cracking owing to the high elastic function. Operando measurements such as GCMS and XRD demonstrate that the PBCS significantly inhibits gas evolution and non-crystallinity formation during cycling. This research shows this novel PBCS Si no longer needs electrolyte additives and another surface coating for preventing those drawbacks in previously mentioned. With this novel PBCS Si material, a high energy density lithium-ion battery contains pure Si or a higher amount of Si can be expected.

Energy harvesting systems based on triboelectric nanomaterials are in great demand, as they can provide routes for the development of self-powered devices which are highly flexible, stretchable, mechanically durable, and can be used in a wide range of applications. Our recent research interest mainly focuses on the fabrication of high-performance triboelectric nanogenerators (TENGs) based on various kinds of nanomaterials. Flexible TENGs exhibit good performances and are easy to integrate which make it the perfect candidate for many applications, and therefore crucial to develop. In this presentation, I firstly introduce the fundamentals and possible device applications of TENGs, including their basic operation modes. Then the different improvement parameters will be discussed. As main topics, I will report transcutaneous ultrasound energy harvesting using triboelectric technology. Implantable medical devices (IMDs) are designed to perform or augment the functions of existing organs by using monitoring, measuring, processing units, and the actuation control. Conventional IMDs are powered with primary batteries that require frequent surgeries for maintenance and replacement. Therefore, IMDs require a new reliable and safe powering system to avoid the need for frequent surgeries. Recently my group demonstrated that ultrasound was used to deliver mechanical energy through skin and liquids and demonstrated that a thin inplantable vibrating triboelectric nanogenerator (TENG) is able to effectively harvest it. Ultrasound TENG (US-TENG) was triggered with an applied 20-kHz ultrasound at 3 W/cm2 reaching 9.71 V(root mean square [RMS]) and 427 ARMS. The measured output current was enhanced two orders of magnitude compared with conventional TENGs, with a similar level of surface charge density, triggered in low-frequency mechanical environments. Interestingly, to experimentally simulate clinical conditions closer to human in the laboratory, we inserted US-TENG under porcine tissue, showing that it fully charged a rechargeable Li-ion battery having a capacity of 0.7 mAh. As the second topic, I will deal with our very recent demonstration of a commercial coin battery-sized high-performance inertia-driven TENG (I-TENG) based on body motion and gravity. In a preclinical test, we demonstrate that the encapsulated device successfully harvested energy using real-time output voltage data monitored via a Bluetooth low-energy information-transmitting system. Details will be presented in the conference site.

Triboelectric energy harvesting technologies have received a substantial amount of attention as they constitute one of the most efficient ways of transforming vibrational and frictional energy into electrical energy, regardless of location and environmental conditions.
One of the most significant advantages of this technology is in the suitability of a very wide range of materials that can be readily incorporated into devices. In order to achieve efficient energy harvesting performance, advances in materials science and nanotechnology have been applied to develop high-performance triboelectric nanogenerators, which have witnessed a tremendous growth in popularity. In this talk, I will discuss materials-driven progress related to triboelectric energy harvesting, with emphasis on the study of materialsrelated operating mechanisms and emergent materials design strategies for highly efficient triboelectric devices. In particular, I will focus on the role of polymer crystallinity and
surface polarization in determining the triboelectric energy harvesting properties of polymeric nanowires. For example, the strong hydrogen bonding in α-phase nylon-11 serves to enhance the molecular ordering, resulting in exceptional intensity and thermal stability of surface potential, and consequently enhanced triboelectric performance compared to other polymorphs of nylon-11. Similarly, tailoring of surface potential in electrospun polymer fibers leads to higher energy harvesting performance in textile-based triboelectric yarns.

The all-inorganic lead halide perovskite without volatile component would be a promising alternative candidate for high efficiency photovoltaics. However, the all inorganic black phase CsPbI3 face the challenges of low room temperature phase stability and relative low efficiency. To enhance the performance and stability of all-inorganic CsPbI3 perovskite, the 2D/3D configuration was introduced to stabilize the black phase CsPbI3. The 2D based on EDAPbI4 help stabilize black phase CsPbI3 to achieve up to >11% efficiency. Furthermore, a facile organic cation surface termination approach was developed to significantly enhance the stability and performance of α-CsPbI3 solar cell with >15% efficiency. The bifunctional stabilization of CsPbI3 with gradient Br doping and organic cation termination finally improve the efficiency of CsPbI3 perovskite solar cells to a record value of 17% with enhanced stabilities. Recently, a concept new beta phase CsPbI3 with better phase stability push the efficiency up to 19%. In all, the CsPbI3 perovskite would be an ideal candidate for stable and efficient perovskite photovoltaics

Halide perovskite solar cells (PSCs) have a typical device structure of thin-film solar cells such as GaAs, CdTe, and CIGS solar cells. The feature point of PSCs is that the thickness of the light-absorbing perovskite layer is much thinner than conventional thin-film solar cells. This requires careful design of local electric field within thin perovskite layer. The electric field can not be only designed by charge-transporting layers at both sides of the perovskite layer but also by the introduction of the interfacial layer between perovskite and CTLs. The formation of halide overlayer on the light-absorbing perovskite layer is a notable strategy to introduce the interfacial layer, which forms a halide double layer. The halide double layer does not only enable to improve power conversion efficiency by the formation of electric field and surface passivation and long-term stability by blocking molecules entering and leaving but can also offer a degree of freedom to choose to appropriate CTL materials on it. In this talk, the strategy of the halide double layer will be introduced, and our related recent results will be discussed.

Stretchability and areal coverage of active devices are key design parameters for wearable or stretchable photovoltaics. Conventional island-bridge structure provides simple but efficient approach for stretchable electronics [1, 2]. However, the trade-off between stretchability and areal coverage is inevitable. All the constraints of traditional island-bridge stem from the fact that stretchable bridge parts and rigid active island parts share limited two-dimensional area.
Three-dimensional arrangement of electronics can enhance the performance of electronic devices. Recent rapid development of 3D printing technology enables three-dimensional design and fabrication of electronic devices with high design flexibility. Recent rapid development of 3D printing techno However, it is still difficult to attain high flexibility and high electric conductivity simultaneously. Flexibility is important for wearable or stretchable applications, and sufficient electric conductivity is also significant to prevent losses.
In this study, we present 3d printer-based fabrication process to attain both high mechanical compliance and electrical conductivity. The suggested process enables ultrastretchable photovoltaics with high areal coverage of active devices. The ultrastretchability and high areal coverage of active devices are achieved with the aid of the conductive 3D-printed kirigami/origami structures.

Organic-inorganic metal halide perovskite solar cells (PSCs) have been improved rapidly, and their photoelectric conversion efficiency (PCE) was increased from 3.8% in 2009 to over 25% in 2020. Since PSCs can be produced easily and inexpensively by simple processes such as printing and coating, the world-wide activities of research and development have been conducted for the commercialization of this technology. However, since the organic substances used in PSCs are unstable with respect to the ambient air, moisture, and heat, there has been a great deal of interest in improving durability, recently. In addition, the components of PSCs, such as hole transport materials (e.g., spiro-OMeTAD) and metal counter electrodes (e.g., Au or Ag), are expensive, and utilization of such materials can be a hindrance for the low-cost PSCs. Using only low-cost materials (without Au, Ag and spiro-OMeTAD), in 2013, the group of Hongwei Han (HUST, Wuhan, China) first reported hole-conductor-free fully-printable multi-porous-layered-electrode perovskite solar cells (MPLE-PSCs). The MPLE-PSCs show extremely high stability against light and heat. In this presentation, the latest progress about MPLE-PSCs will be shown in our group (for example, stability at 120°C for 4500 h, and at 85°C-85%RH for 2000 h).

Metal halide perovskites (MHPs) for photovoltaic applications have the general stoichiometry formula of ABX3, with A as the monovalent organic or inorganic cation, B as the divalent lead or tin cation, and X as the halide anion. The A cation itself does not directly contribute to the band edge states. However, the A cation was found to significantly influence the physical, chemical, and optoelectronic properties of MHPs. Resultingly, engineering of the A cation has enabled important breakthroughs to enhance the performance and stability of perovskite solar cells (PSCs). In this presentation, I will report novel ‘A’ site cation engineering strategies for enhancing power conversion efficiencies (PCEs) and stability of the PSCs. Incorporation of over- or under-sized ‘A’ was found to induce strain in the bulk lattice of the MHPs, allowing for modulation of ion migration energetics in the bulk lattice. We demonstrate the induced strain can enhance the activation energy barrier for ion migration to significantly improve operational stability of the PSCs. In addition, I will also report utilization of bulky organic cationsto passivate surface defects of the MHP thin films. The rational strategies for maximizing the surface passivation effects with minimized side effects will be presented.

A synergistic passivation mechanism of a mixed-salt treatment through surface reconstruction engineering is unraveled. This strategy reduces defects and suppresses ion migration of the perovskite interface, leading to an enhanced photovoltaic performance meanwhile presenting outstanding operational stability. More generally, the proposed mixed-salt system provides a wider way of designing functional passivation materials which gets benefits from its synergistic effect.

In addition to mobile electrons and holes, the mobile ions in metal halide perovskites redistribute under an applied electric field. It negates many benefits of standard spectroscopic techniques to quantify mobility, such as nanosecond to millisecond transient methods, time-of-flight and space charge limited current measurements. Indeed, an accurate estimation of charge carrier density is hindered by early-time recombination, the branching ratio of excitons to free-carriers and sensitivity to short-range conductivity. It is also important to understand the long-range charge transport within the metal halide perovskite for optimisation of operating devices, where the charges have to travel over on the order of microns, and if these properties change in different carrier density regimes, or through different methods of processing the films. Here this presentation introduces applied methodologies and also highlights an advanced optical and electrical methodologies: Photoinduced transmission and reflection (PITR), Transient photoconductivity (TPC) and Pulsed-voltage space charge limited current (PV-SCLC). With these methods, we accurately estimated the internal free-carrier density during photo-excitation, accounting for both early-time recombination and exciton-to-free-carrier branching ratios to determine long-range charge carrier mobility in metal halide perovskite thin films and single crystals, to be reliable value over many orders of magnitude of charge density. We believe this study is the accurate evaluation of photo-induced long-range mobility of metal halide perovskites, and therefore represents a powerful handle for future optimisation of perovskite solar cells and optoelectronic devices.

With rapid advances in the development of new conjugated polymers, non-fullerene acceptors, the power conversion efficiency (PCE) of organic photovoltaics (OPVs) has been increased over 17%. However, a major drawback for the commercialization of OPVs is their long-term stability under continuous operation. Especially, OPVs suffer from a rapid decrease in PCE during initial device operation, which is known as the “burn-in loss”. It is considered that the origin of the burn-in loss is mainly related with the instability of the heterojunction morphology at bulk and/or interface. In this contribution, I would like to introduce a strategy to improve heterojunction morphology through the construction of heterojunction by sequential deposition of conjugated polymer donor and conjugated small molecule acceptor.

The tandem solar cells, which based on dual junctions combining wide-bandgap top cells (e.g., ~1.7–1.9 eV) and narrow-bandgap bottom cells (e.g., ~0.9–1.3 eV) are considered as an effective strategy to overcome the Schokley-Queisser (S-Q) limit (~31-33%) of single-junction solar cells. Organic-inorganic metal halide perovskite (PVSK) materials is one of the most promising candidates for the top- and bottom-cell in tandem devices (e.g., PVSK/PVSK, PVSK/Cu(In,Ga)Se2 (CIGS), and PVSK/Si) owing to their flexible bandgap-tunability, low-cost processing, and various
formation routes like spin-coating, blade-coating, vacuum deposition. One of the critical challenges in developing tandem devices using perovskite is to prepare highly efficient wide- or narrow-bandgap perovskite solar cells (PSCs) for top- and bottom-cells, respectively. Among the various efforts such as composition engineering, morphology control, contact layer improvement, and defect passivation for improving the performance of PSCs, the formation of a 2-dimensional (2D) passivation layer using large organic cations (e.g., butylammonium or phenethylammonium) have been considered one of the most promising approaches. However, some challenges have led to lower performance in 3D/2D mixed PVSK due to the limitation of charge transport caused by the long and bulky organic cation from the 2D passivation layer. This presentation introduces the various strategies like cation/anion engineering in 2D parts and dipole engineering to demonstrate a highly efficient 3D/2D PSCs with various bandgap (1.23 eV and 1.68 eV). Based on our strategies, we finally demonstrated highly efficient and stable PVSK based tandem solar cells with various kinds of bottom cells combination like Perovskite, CIGS, and Si.

Aqueous zinc-based flow batteries are an attractive option for energy storages system due to their inflammability and high energy density. However, Zn dendrite formation, which causes internal short circuit and capacity drop, limits long-term operation of Zn-based batteries. Uncontrolled Zn nucleation/growth or Zn-ion transport leads to inhomogeneous Zn reaction and triggers dendritic Zn growth. In this aspect, advanced engineering of the Zn/substrate and Zn/electrolyte interface, which can control these processes, is strongly demanded. In this talk, we present that an atomistic-designed carbon current collector and a structured interlayer on Zn electrode can control these interfacial processes for inducing dendrite-free Zn deposition. By experimental and computational analysis, the working mechanism of the advanced interfaces is elucidated. The performances and durability of the Zn batteries exploiting the advanced interfaces demonstrate the efficacy of the advanced interfacial engineering on achieving reversible Zn electrode.

The ongoing surge in demand for flexible/wearable electronics, self-powered systems, soft robotics, and Internet of Things (IoT) has inspired the relentless pursuit of form factor-free, high-performance power sources that can be monolithically and seamlessly integrated with various electronic devices. From the viewpoint of cell design and architecture, conventional assembly and materials have pushed the power sources to lack of variety in form factors, thus imposing formidable challenges on their integration into versatile-shaped electronic devices. This talk describes a new class of nanoprinted artistic power sources, with particular attention to their design diversity and performance compatibility with newly emerging complex-structured electronic devices. The printed power sources are fabricated directly on arbitrary objects of complex geometries through a variety of simple, low-cost and scalable nanoprinting processes. Their salient features include various form factors, shape conformability, and monolithic integration with devices of interest. A key-enabling technology for the nanoprinted power sources is the design of battery inks (in particular, electrode and electrolyte inks), with a focus on their rheology and electrochemistry. Our research interests are directed to discussing effects of the battery inks on printing processability, nanostructure (focusing on bicontinuous ion/electron transport channels), artistic versatility, and electrochemical performance of the resulting nanoprinted power sources. We envision that the nanoprinted power sources open a new avenue towards form factor-free/monolithic integrated power sources with object-tailored design versatility and dimensional conformability.

All-solid-state lithium batteries (ASSLBs) have the potential to increase energy density, improve safety, and allow for lower manufacturing costs compared to conventional, liquid-based Li-ion batteries. In this talk, I will first present cobalt-free solid-state Li batteries using 50 um-thick sulfide-based solid electrolyte (SE). We demonstrate a high-energy ASSLB using an organic cathode material. The use of organic materials in ASSLBs brings many new possibilities to the technology due to their unique feature set of material availability, mechanical properties, electrode reaction characteristics. Furthermore, the thickness of SE layer dictates the cell-level energy density and it is desirable to make the SE layer as thin as possible while maintaining uniformity and defect-free. We show a strong correlation between the solid loading of dispersions and the quality of tape-casted thin SE films. We developed an imaging technique to characterize large areas of films and to quantify their quality by using histograms of the tonal contrast within the images. Stable cycling of Li metal could be realized when inserting a unique designed interlayer in between solid electrolyte and Li metal. In the second half of this talk, I will present an air-free vessel design for operando diagnosis of ASSLBs. The vessel is equipped with a micro-cell mount where electrochemical tests are performed in situ. Heating and pressure applying/sensing modules are also integrated in the platform. The air-free design allows transfer of an air-sensitive ASSLBs between different analytical instruments. We demonstrate successful operando characterizations of microstructures under electron microscopy and optical microscope. A consolidated in situ structural-chemical-mechanical diagnostic platform is under development that will provide unprecedented insights into the failure mechanisms of ASSLBs.

Acknowledgment: This work is supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Vehicle Technologies Program under Contract DE-EE0008234 and DE-EE0008864 (Program manager: Tien Duong).

Silicon (Si) has the maximum capacity (> 4000 mAh g-1) compares with the conventional graphite (300-350 mAh g-1), which can dramatically increase the energy density of the battery. However, due to some drawbacks on Si material such as electrochemical irreversibility and volume expansion on alloy reaction, pure Si cannot be used in large quantities in the anode electrode, approximately 3~8 wt% only in commercial products. In this research, a novel method for pure Si material has been developed, a polymer brush modified core-shell structure (PBCS) by hydrosilylation reaction on Si nanoparticles. According to the results, the PBCS structure provides three significant functions on Si particles because of the effects of hydrogen bonding such as good dispersion in the slurry, a protection during cycling, and excellent conductivity for high-rate tests. The polymer brush is fabricated by the acrylic acids in which the hydrogen bonding effects between each carbonyl groups are used to enhance lithium-ion diffusion and the adjustment of attraction and repulsion in between particles. The PBCS Si electrode shows the first columbic efficiency is 87.1%, the retentions are 92.5% (0.1C/ 0.1C) for 200 cycles and 86.2% (0.5C/ 0.5C) for 400 cycles, respectively. The TEM and TXM results display that the PBCS structure significantly protects the nano Si from cracking owing to the high elastic function. Operando measurements such as GCMS and XRD demonstrate that the PBCS significantly inhibits gas evolution and non-crystallinity formation during cycling. This research shows this novel PBCS Si no longer needs electrolyte additives and another surface coating for preventing those drawbacks in previously mentioned. With this novel PBCS Si material, a high energy density lithium-ion battery contains pure Si or a higher amount of Si can be expected.

Electrifying transportation systems to reduce our dependence on fossil fuels is a critical priority to address climate change, and more powerful and affordable batteries are key to accelerate the adoption of zero-emission electric vehicles (EV). Recently, we developed a stable, fast-charging battery that comprises i) a lithium metal anode, ii) a heavy-metal free cathode involving iodide conversion reactions, and iii) a stable liquid electrolyte with high flash point. The unique combination of these materials has demonstrated remarkable performance including outstanding power density, fast charging time, and prolonged cycle life, surpassing conventional lithium-ion batteries. In this talk, the fundamental electrochemistry and interfacial phenomenon responsible for this new battery system’s excellent performance will be discussed along with our strategies to accelerate the process of further improvement and optimization of this battery system.

A charging time is one of the key features of the batteries which is used in electric vehicles (EV). One must apply larger current to fill the same energy to reduce the charging time because the amount of applying current is inversely proportional to the charging time. It is necessary to ensure rapid kinetics of electrode materials for accommodate the massive Li flux. Improving charging characteristics of cathode materials has been intensively studied by our research group using the most popular materials, NCM series. The shape of NCM particle was designed with core-shell structure with different composition, which is the Ni-rich core and the Co-rich shell. In this talk, we present that unique shape of precursors with Co-rich surface resulted to the large surface area and lower Ni to Co ratio surface of active materials. These active materials show superior electrochemical performance to the normal NCM materials under the fast-charging condition.

Micro-electrochemical energy storage devices with in-plane geometry, e.g., micro-supercapacitors (MSCs) and micro-batteries (MBs), are a new class of miniature energy storage devices for various microelectronics. Two dimensional (2D) materials with the advanced merits of ultrathin flat structure, high specific surface area, and excellent mechanical characteristics, are one of the perfect candidates for planar MSCs and MBs matching well with the in-plane geometry to boost the performance. In this talk, our recent progress on 2D materials based planar micro-electrochemical energy storage devices will be reported. First, high capacitance 2D materials of such as electrochemical exfoliated doped graphene, MXene, metal oxides and mesoporous polymers are successfully prepared by the strategies of electrochemical exfoliation, liquid exfoliation, graphene template, and supramolecular self-assembly methods. Second, high-performance MSCs and MBs for different integrated systems are further explored. Via modulating highly stable and conducting 2D materials (e.g., graphene, MXene)-based inks with outstanding rheological, electrical and electrochemical properties, the planar integrated MSCs and MBs are fabricated via a universal, cost-effective, industrially applicable screen-printing strategy. The highly conductive inks can be used as current collectors, microelectrodes and interconnects simultaneously, and the all-solid-state planar integrated MSCs can achieve ultrahigh output current/voltage through series or parallel connection. Moreover, planar integrated microscale energy storage systems with different application scenarios are exploited, like the prototype planar integrated system of MSC and NH3 sensor, the all-flexible MXene-based self-powered integrated system composed of a tandem thin-film silicon solar cell, a MXene-Lithium ion MBs or a MXene-MSCs, and a MXene hydrogel pressure sensor on a co-planar substrate. The MXene-based self-powered integrated system is demonstrated that sensitively monitors the bending of body movement with a fast response of 35 ms. What’s more, this type of electrochemical microdevices integrates energy generation/harvests, energy storage, and energy consumption in one system, and can be widely used in many demands.

Photoelectrochemical water splitting presents an attractive strategy to produce hydrogen gas as an alternative clean fuel in an environmentally benign and sustainable manner. The key component of a photoelectrochemical cell is a semiconductor electrode (photoelectrode) that absorbs solar light to generate, separate, and transport charge carriers to the semiconductor/electrolyte interface to participate in desired chemical reactions. The electron-hole separation and interfacial charge transfer of the photoelectrode are considerably affected by the interfacial energetics between the photoelectrode and the electrolyte and/or between the photoelectrode and the buffer, protection, or catalyst layers; hence, the interfacial properties of a photoelectrode are as important as the bulk properties of the photoelectrode.
To date, strategies for altering the atomic arrangement at the photoelectrode surface that do not involve extrinsic doping have mainly involved changing the semiconductor surface facets. However, for ternary oxide photoelectrodes with a formula of AxByOz, there exist numerous ways to terminate the surface even for the same facet. For example, the surface can be terminated with A-O or B-O, and the surface A:B ratio may be different from the bulk A:B ratio. In fact, if not grown as single crystals, AxByOz photoelectrodes can have an A-rich or B-rich surface depending on the synthesis method, which can affect their photoelectrochemical properties. However, despite being important and ubiquitous, the effects of surface termination/composition on a ternary oxide photoelectrode have not been systematically studied, and the atomic origin of their effects on interfacial energetics and photoelectrochemical properties have not been elucidated.
In this presentation, we will discuss the effects of surface termination/composition on the interfacial energetics and photoelectrochemical properties of photoanodes using BiVO4 as an example. We will compare epitaxially grown BiVO4 photoelectrodes with V-rich and Bi-rich (010) exposed facets and demonstrate that the surface Bi:V ratio has a considerable effect on the surface energetics and photocurrent generation of BiVO4 even for the same (010) facet.

Photocatalytic water splitting is a challenging reaction because it is an ultimate solution to resources, energy, and environment issues. Photocatalytic CO2 fixation has also attracted attention. These can be regarded as artificial photosynthesis, because light energy is converted to chemical energy. In the present paper, I introduce various metal oxide and sulfide photocatalysts for the water splitting and CO2 reduction.
AgTaO3 and Na0.5Bi0.5TiO3 of valence-band-controlled metal oxide photocatalysts gave 40% at 340 nm and 5.1% at 350 nm of apparent quantum yields, respectively. SrTiO3:Rh and several metal sulfides of a H2-evolving photocatalyst and BiVO4 of an O2-evolving photocatalyst constructed various type of Z-schematic photocatalyst systems with Fe3+/Fe2+, [Co(bpy)3]3+/2+, and a conductive reduced graphene oxide (RGO) as an electron mediator, and even without an electron mediator. Ag cocatalyst-loaded ALa4Ti4O15 (A = Ca, Sr, and Ba) and tantalates photocatalysts such as NaTaO3:Ba with 3.79–4.1 eV of band gaps show activities for CO2 reduction to form CO and HCOOH in an aqueous medium. We also constructed a Z-scheme system using CuGaS2 of a CO2-reducing photocatalyst with BiVO4 of an O2-evolving photocatalyst and RGO of an electron mediator for CO2 reduction using water as an electron donor.

Conjugated polymers have recently emerged as promising candidates for photocatalytic H2 production owing to their structural designability and functional diversity. However, limited by the fast recombination of photoexcited electrons and holes, their H2 production rates usually fall far behind expectations. To this end, we for the first time design molecular heterostructures of covalent triazine frameworks to facilitate the charge carrier separation and promote the photocatalytic H2 production. Benzothiadiazole and thiophene moieties are selectively incorporated into the covalent triazine frameworks as the electron-withdrawing and electron-donating units respectively via a rationally designed sequential polymerization strategy. Resultant hybrids exhibit much improved charge carrier separation efficiency as evidenced by a range of photophysical and electrochemical characterizations. Most impressively, a significant H2 evolution rate of 6.6 mmol g-1h-1 is measured for the optimal sample under visible light irradiation (λ>420 nm), which is far superior to most other conjugated polymer photocatalysts reported in literature.

Semiconductor materials hold the key for efficient photocatalytic and photoelectrochemical water splitting. In this talk, we will give a brief overview of our recent progress in designing semiconductor nanomaterials for photoelectrochemical energy conversion including solar hydrogen generation. In more details, we have been focusing on a couple of aspects; 1) band-gap engineering, facet and oxygen vacancy control of low-cost metal oxide based semiconductors including TiO2, Fe2O3, BiVO4 and Cu2O for new photoelectrode design, and 2) the combination of high performance photoelectrodes with hybrid perovskite solar cells towards unassisted water splitting process with solar-to-hydrogen conversion efficiency of >6.5%. The resultant material systems exhibited efficient photocatalytic performance and improved power conversion efficiency in solar cells, which underpin sustainable development of solar-energy conversion application.

Solar-chemical production inspired from nature has attracted substantial attention due to a need for developing sustainable future energy as well as chemical resources. In order to achieve a highly efficient solar energy to chemical conversion device using CO2 and water as feedstock the development of several important components such as photoelectrode, catalytic electrodes, membrane, etc. is required. Among them, this lecture focuses on a Cu(InxGa1-x)(SySe1-y)2 (CIGS) thin film photovoltaic technology, which is a very attractive candidate for photoelectrode application of solar-chemical production system because they are durable enough and cost effective with high efficiency. To make the CIGS photovoltaics more cost effective solution processed CIGS thin film preparation has been suggested and developed. In spite of several successful demonstrations most solution based methods resulted in lower photovoltaic performance than vacuum based counterpart to date. In this presentation several strategies for realizing highly efficient and useful solution processed CIGS thin film photovoltaics will be introduced. They include multi-stage paste coating method, doping method, and nanostructuring method that have been being developed in our laboratory.

It is of great importance to reduce the amount of noble metals in the chemical industry. In this sense, single atom or atomically dispersed catalysts have attracted much attention due to high metal utilization and unique catalytic property. In this presentation, we will show a combination of density functional theory (DFT) and experimental approaches to explore the stability and electrocatalyic activity of a wide range of metal single atoms on a TiC support. We also tuned and enhanced the activity of Fe-N-C, atomically dispersed electrocatalyst, by givign the effect of electron withdrawing/donating functionalities.

The monolayered 2D nanosheets of layered inorganic solids (layered metal oxides, layered double hydroxides, layered metal chalcogenides, and graphene) have attracted intense research interest as versatile precursors for synthesizing highly efficient hybrid catalysts applicable for renewable energy technologies. A great diversity in the chemical compositions and crystal structures of 2D inorganic nanosheets provides these materials with a wide spectrum of physical properties and functionalities. The monolayered 2D inorganic nanosheets can be synthesized by soft-chemical exfoliation reaction of the pristine layered materials and used as building blocks for exploring high-performance hybrid photocatalysts and electrocatalysts. In the resulting hybrid catalysts, these 2D nanosheets act as catalytically active components and/or conductive additives for improving the catalyst performances. In this talk, several examples of monolayered 2D nanosheet-based photocatalysts and electrocatalysts will be presented together with the relationship between catalyst performance and chemical bonding nature.

Development of DNA-based molecular machines and robots has attracted much attention due to their promising applications in medical, agricultural, and environmental technologies. DNA nanodevices and nanomachines have been constructed based on DNA sequence design, which enables us to program functions and to control the devices and machines according to the program. It is expected to construct cell-like multifunctional and intelligent molecular robots by extending the DNA nanotechnology. In this presentation, we will introduce our recent progress on DNA droplet technology. Cell-sized functional microdroplets have been constructed with DNA nanostructures, and their dynamical functions and behaviors have been controlled in a programmable manner. Here, we will report two types of DNA-based droplets technology: (i) DNA origami-based emulsion and (ii) DNA liquid droplet.
First, we will report a DNA origami nanoplate-based emulsion with designed nanopore function [1]. We constructed DNA-nanoplate-stabilized emulsion because DNA nanoplate produced by DNA origami method will have the design programmability. Here, we generated hexagonal DNA nanoplate using DNA origami technology. The DNA nanoplates were amphiphilized by the modification of the only one face of the hydrophilic DNA nanoplate with hydrophobic cholesterol groups. An aqueous solution of the amphiphilic DNA nanoplate was put into an oil phase of mineral oil, and then the two-phase solution was emulsified. By the microscopic observation, microemulsion stabilized with the amphiphilic DNA nanoplates was confirmed. Finally, we confirmed the ion transportation between contacted two droplets stabilized with the amphiphilic DNA nanoplates with a nanopore using a microdevice for ion current measurement. This result suggests that the integration of programmed function on DNA origami nanoplate-based emulsion.
Second, we will report a DNA droplet produced through liquid-liquid phase separation of a DNA nanostructure (named DNA Y-motif) solution [2]. In this study, we found that the phase behavior of DNA Y-motif could be controlled based on the sequence design of the terminal sticky end of the branches of DNA Y-motif. Also, we found that the fusion of the liquid-like DNA droplets could be controlled based on the sticky-end sequence and that the autonomous fission of DNA droplet could be achieved with enzymatic reaction. Finally, we demonstrated protein positioning in the DNA droplets based on the sequence. These results show that the condensed soft matter phase of DNA nanostructure can be used as a molecular robot body that has the integration ability of functional molecules such as proteins.
We believe that these technologies will promote the construction of molecular robots with integrated functions. Also, in the future, by the combination with biomembrane technology such as a DNA cytoskeleton [3] and the integration with electrical control device such as a computer-controlled artificial cell reactor [4], the functional molecular robots will be helpful in many fields mentioned above.

[1] Ishikawa, D., et al., Angew. Chem. Int. Ed., 58, 15299-15303 (2019).
[2] Sato, Y., et al., Science Advances, Vol. 6, no. 23, eaba3471, (2020).
[3] Kurokawa, C., et al., Proc. Natl. Acad. Sci. USA, 114(28), 7228-7233 (2017).
[4] Sugiura, H., et al., Nature Commun., 7, 10212 (2016).

In this study, we designed polymeric gene carrier consisting of polymer and drug, and applied it to anti-cancer therapy. We prepared hypoxia-responsive mesoporous silica nanocarrier for an enhanced immunocancer therapy assisted by photodynamic therapy. Nanocarrier was designed as a hypoxia-responsive transforming carrier to improve the intracellular uptake of nanocarriers and the delivery of adjuvants to DCs.
As a cell therapy strategy, we used tumor-homing ability of natural killer (NK) cells for the delivery of drug-loaded polymeric micelle. NK cells are decorated with the immunologican synapse environment-responsive micellar system to ensure the release of payload when they attack cancer cells. Harnessing the intrinsic mechanism for the recognition of abnormal cells and the tumor-homing effect of NK cells limit the adverse systemic effects of chemotherapeutic drugs. The overall design concept, physicochemical properties of polymeric micelles, in vitro behaviour and in vivo tumor-targeting ability will be presented in this presentation.
In this study, we also developed novel nitric oxide (NO) delivery system using catecholamine and diazeniumdiolates. Simple two-step reactions comprising catecholamine and diazeniumdiolates enable virtually any material surfaces to release NO with appreciable storage. The modified surfaces showed the antibacterial activity without cytotoxicity. We also prepared NO-scavenging hydrogel for alleviating inflammatory disease such as rheumatoid arthritis (RA). We developed a NO-responsive macro-sized hydrogel by incorporating an NO-cleavable crosslinker (NOCCL); we further evaluated the effectiveness of the NO-scavenging nano-sized hydrogel for treating RA. The NO-Scv gel reduced inflammation levels by scavenging NO in vitro and significantly suppressed the onset of RA as observed in vivo in a mouse RA model.

A microneedle array patch (MAP) has been studied as a means for delivering drugs or vaccines and has shown superior delivery efficiency compared to the conventional transdermal drug delivery system. Recent advancements in the development of MAPs, is reviewed with a focus on their size, shapes, and materials in preclinical and clinical studies for pharmaceutics and vaccines.
We classified MAPs for drug delivery into four types: coated, dissolving, separable, and swellable. We covered their recent developments in material, fabrication process and geometries in preclinical and clinical studies. We tried to determine how these factors could affect the strategies and efficacy of drug delivery.
As examples of QuadMedicine vaccine MAPs (microneedle array patch), Hepatitis B (HepB)Vaccine MAP, influenza (Flu) virus vaccine MAP and canine influenza virus vaccine MAP were introduced. Vaccine MAPs are effective as intramuscular administration (IM) administration of conventional vaccines. HepB vaccine MAP and Flu vaccine MAP showed comparable efficacy with those by IM administration and they showed improved thermal stability and storage stability than liquid formulation of conventional vaccines. Canine Flu vaccine MAP could induce comparable immune response with that by IM administration. The manufacturing process of QuadMedicine could achieve the dose uniformity and low cost of MAP. QuadMedicine vaccine MAP can provide the innovative platform to eradicate the infectious disease, which threatens public health.
The MAP is an excellent drug delivery system that has provided desirable pharmacokinetics and pharmacodynamics in many studies. Also MAP provides solutions to overcome the previous vaccine formulation and administration method. The design of MAPs needs to be determined based on what properties would be effective for the target diseases and purposes. In addition, in preclinical studies, it is necessary to consider not only the novelty of the formulations, but also the feasibility of clinical application. With these considerations, the microneedle array patch will be a better option for drug delivery.

The lanthanide-based nanocrystals (NCs) have tremendous potential for designing multimodal imaging probes. The f-block lanthanide elements exhibit unique optical and magnetic properties, including upconversion luminescence and paramagnetic behaviors, which can be further manipulated by control of size, shape, and compositions. First, I will describe novel materials chemistry to synthesize luminescence upconverting metal halide NCs. The synthesis of metal halide NCs is performed via injection-free, heating-up method in the presence of a solvent mixture with a high boiling point. We present synthetic method to systematically tailor structure and composition of phase-pure metal halide NCs and investigate upconverting photoluminescence properties by lanthanide doping. In addition, we represent synthesis of pH-responsive upconverting luminescence via dye-modification. We study the near-IR to visible two-photon upconversion of NCs doped with lanthanide elements. The surface modification of upconverting NCs with pH-sensitive organic probes to tailor their luminescence properties depending on the pH of solution.

Several topics of inorganic nanoparticles intended for applications in biology will be discussed. First, the general issue on how reliable nanoparticle properties can be related to their biological impact will be discussed. References: S. Ashraf, A. H. Said, R. Hartmann, M.-A. Assmann, N. Feliu, P. Lenz, W. J. Parak, "Quantitative Particle Uptake by Cells as Analyzed by Different Methods", Angewandte Chemie 59, 5438-5453 (2020); H. Yan, M. Cacioppo, S. Megahed, F. Arcudi, L. Dordevic, D. Zhu, M. Prato, W. J. Parak, N. Feliu, "Influence of the chirality of carbon nanodots on their interaction with proteins and cells", submitted to Nature Communications, in revision. Second, one application of plasmonic nanoparticles in the direction of photothermal heating will be discussed. This will involve in particular the excitation of intracellular calcium waves. Reference: D. Zhu, L. Feng, N. Feliu, A. H. Guse, W. J. Parak, "Stimulation of local cytosolic calcium release by photothermal heating for studying intra- and inter-cellular calcium waves", Advanced Materials, in press.

With profound advances in immune-oncology, cancer immunotherapy is now considered the fourth pillar of cancer therapy, joining the ranks of surgery, radiotherapy, and chemotherapy. However, only a small subset of cancer patients responds to cancer immunotherapy. While the combination of multiple immune checkpoint blockers generally improves the clinical responses, this can lead to severe immune-related adverse events that result in clinical manifestations of dermatitis, colitis and hepatitis. Thus, to fully realize the potential of cancer immunotherapy, new approaches are needed to amplify anti-tumour T-cell immune responses, to convert cold tumours into hot tumours, and to sensitize tumours to immunotherapies with minimal off-target toxicity and immune-related adverse events. Here, we present new biomaterial-based strategies for amplifying anti-tumor immune responses and sensitizing tumors to immunotherapies in a safe and effective manner. Briefly, we show that lipid-based nanodiscs can efficiently co-deliver antigen and immunostimulatory molecules to draining lymph nodes and elicit potent CD8+ cytotoxic T lymphocyte responses directed against tumor antigens, leading to substantially enhanced anti-tumor efficacy in multiple murine tumor models, including colon carcinoma, melanoma, and glioblastoma multiforme. We have also demonstrated their efficacy in non-human primates. In a second research thrust, we are developing new biomaterials for in situ modulation of the gut microbiome for regulation of local and systemic immune responses. We will share our latest results showing the therapeutic potential of our gut modulation approach in the context of improving the safety and efficacy of immune checkpoint blockers. Owning to the facile manufacturing process, robust therapeutic efficacy, and good safety profiles, our biomaterial-based approaches may offer powerful and convenient platforms for improving cancer immunotherapy and cancer patient outcomes.

Nanostructures such as nanosheets, and nanoballs have been studied for delivery of chemical anticancer drugs and oligonucleotides. Although numerous studies have been done, the translation to commercialized products has not been successful. We aimed to design nanosystems which can modulate the immune microenvironment of tumors. For immunotherapy, adjuvant-loaded nanoparticles were modified with immune checkpoint blockade. In tumor-bearing xenograft, the surface-modified nanostructures provided selective activation by cleavage of fibroblast-associated protein at tumor microenvironment, and greater antitumor effect than other comparison groups. Moreover, we designed an adjuvant-entrapped nanoparticle which can assemble with tumor antigens in situ for effective activation of immune cells. The systemic administration of adjuvant-entrapped nanoparticles with near infrared light irradiation increased the activity of immune cell infiltration to the tumor cells, and inhibited tumor growth. In another study, we used nanomaterials for modulating the metabolic features of T cells in the tumor microenvironments. T cell-specific delivery and modulation of lipid metabolism enhanced the capability of T cells to recognize and attack tumor cells. Taken together, these studies suggest the potential of nanomaterials for modulating the immune microenvironments of tumors.

Recently, reactive oxygen species (ROS) have been highlighted as one of the key players that underlie the acquisition of the various hallmarks of cancer. As ROS are associated with all stages of cancer, their applications in cancer treatment based on the following concentration‐dependent implications have attracted much attention: (1) low to moderate levels of ROS as key signaling molecules, (2) elevated levels of ROS in cancer cells as one of the unique characteristics of cancer, and (3) excessive levels of ROS as cytotoxic agents.In our group, considering ROS from a different point of view, various cancer nanomedicines have been designed to achieve spatiotemporal control of therapeutic action, the main research focus in this area. The integration of nanomedicine and ROS‐mediated therapy has emerged as the new paradigm in the treatment of cancer, based on promising proof‐of‐concept demonstrations in preclinical studies. Further efforts to ensure clinical translation along with more sophisticated cancer nanomedicines to address relevant challenges are expected to be made in the coming years.

Atherosclerosis is a chronic inflammatory disease that progresses with the accumulation of interrelated cholesterol crystals (CC) and macrophages in the arterial wall. These are not only the main components of atherosclerotic plaques, but also key inflammation-triggering sources that promote their own accumulation. However, existing therapeutics have not achieved effective removal of both CC and macrophages from plaques for the treatment of atherosclerosis. In this talk, I will introduce a new class of nanomedicine that delivers the anti-inflammatory drug to plaques and carries away cholesterol from there at the same time for effective anti-atherosclerosis therapy. In mouse models of atherosclerosis, systemically injected nanomedicine accumulates preferentially in atherosclerotic plaques and significantly reduces the amount of cholesterol crystals and the number of macrophages, thus leading to inhibition of atherosclerotic plaque development and regression of the established plaques. I believe that this nanomedicine offers a powerful therapeutic option for the treatment of atherosclerosis.

Cancer immunotherapies that harness the body's immune system to combat tumors have received extensive attention and become mainstream strategies for treating cancer. Despite promising results, some problems remain, such as the limited patient response rate and the emergence of severe immune‐related adverse effects. For most patients, the therapeutic efficacy of cancer immunotherapy is mainly limited by the immunosuppressive tumor microenvironment (TME). To overcome such obstacles in the TME, the immunomodulation of immunosuppressive factors and therapeutic immune cells (e.g., T cells and antigen‐presenting cells) should be carefully designed and evaluated. Nanoengineered synthetic immune niches have emerged as highly customizable platforms with a potent capability for reprogramming the immunosuppressive TME.
In this study, nano‐biomaterials that could modulate the immunosuppressive TME in a spatiotemporal manner for enhanced cancer immunotherapy were rationally designed and systematically investigated [1-6]. Local and extended release of immunomodulatory drugs from nanoengineered synthetic immune niches such as immuneCare-DISC and iGel depleted immunosuppressive cells, while inducing immunogenic cell death and increased immunogenicity. When nanoengineered synthetic immune niches were applied as a local postsurgical treatment, both systemic antitumor immunity and a memory T cell response were generated, and the recurrence and metastasis of tumors to lungs and other organs were significantly inhibited. Reshaping of the TME using synthetic immune niches also reverted non-responding groups to checkpoint blockade therapies into responding groups. The nanoengineered synthetic immune niches are expected as an immunotherapeutic platform that can reshape immunosuppressive TMEs and synergize cancer immunotherapy with checkpoint therapies, with minimized systemic toxicity.

Herein, we demonstrate theoretical and experimental evidence for 4-inch-scale, high-quality graphene grown directly on 10 nm-thick-Ti-buffered substrates via plasma-assisted thermal chemical vapor deposition (PATCVD) at temperatures below 150 °C. The transfer-free monolayer graphene revealed predominant flexible and stretchable properties with a sheet resistance as low as 80  5.0 □- 1 and a giant average domain size of ~ 380 m. The in-situ 4-layers stacked graphene showed an ultralow resistance of ~ 6 □-1 by a self-p-doping under ambient conditions. Graphene-field effect transistors (FETs) fabricated on polydimethylsiloxane (PDMS) substrates revealed an extraordinary hole mobility of ~ 21,000 cm2V-1s-1 at a gate voltage of - 4V regardless of the channel lengths. They retained ~ 87% of their original mobility at 140% strain parallel to the direction of charge transport and showed a superb mechanical robustness when stretched repeatedly for 5,000 cycles under 120% parallel strain. Monolayer graphene grown on PDMS, which did not undergo plastic deformation, exhibited unprecedented flexibility at a static tensile strain of 15% (radius of curvature: 0.6 mm) and for 3104 bending cycles under a tensile strain of 11% (radius of curvature: 0.9 mm). Large-area, high-quality monolayer graphene synthesized directly at low temperatures could enable the practical development of transparent, flexible, and stretchable electronics.

Artificial Intelligence (AI) technology based on artificial neural networks is making a huge business and socioeconomic impact, changing our daily life. With an expectation of achieving a brain-like efficiency and large performance gain, there has been increasing interest to implement artificial neural networks using novel non-volatile memory devices. Novel cross-point array architectures based on resistive memory devices, which can be operated in a massively parallel manner, have shown potential to achieve a large acceleration in AI computation. For realization of such architectures in hardware, the specifications for synaptic devices are revealed to be different in many aspects with those for traditional memory devices, necessitating new material systems and device designs [1] for efficient AI computation. In this talk, I will overview the recent progress and effort to achieve ideal synaptic device characteristics for novel neuromorphic architectures, as exemplified in our recent experimental results on resistive memory devices (RRAM), capacitor-based approach, and 3-terminal ionic switching devices.

Layered topological materials such as topological insulators (TIs) and Weyl semimetals are a new class of quantum matters with large spin-orbit coupling. We reveal spin textures of such materials using the bilinear magneto-electric resistance (BMR) and photocurrent mapping. Topological surface states (TSS) dominated spin orbit torques are identified, and magnetization switching at room temperature is demonstrated in a topological material/ferromagnet (FM). Magnon-torque-driven magnetization switching is also demonstrated in the TI/NiO/FM devices at room temperature. In addition, topological materials can provide an alternative for rectification or frequency doubling. Looking towards the future, we hope that these studies will spark more works on harnessing spin currents at topological material/magnet interfaces and energy harvesting applications from topological materials.

Quantum computer enables to solve complex problems faster than classical computer using quantum phenomena such as superposition and entanglement. Superconducting circuit is one of the leading platforms for realizing the quantum computer. The superconducting quantum computing systems including qubit can make circuit design with various parameters and are proper to expand to large-scale quantum system. In this talk, I introduce the superconducting quantum computing system in KRISS and present the latest progress on superconducting multi-qubit system. We characterized the qubit in the scalable quantum system and estimated the error rate of quantum gates. Also, we reconstructed various quantum states using single and two qubit gates.

Intercalation is a century-old process of molecule insertion into layered materials. The advent of single-layered 2D materials has provided new opportunities to understand and apply intercalation processes. In this talk, I will give an overview of the potential of atomically thin intercalants towards future nanoelectronics.
First, I will demonstrate the ordering of intercalants in the graphene van-der-Waals gap and its enabling characteristics for producing novel 2D materials. Through a planarized solid-state chemical reaction of intercalants and a crystal surface, transition-metal monochalcogenides of different compositions could be produced with atomic thickness precision. Thus-produced 2D crystals exhibit commonly unattainable thermodynamic
phases with ultra-large phase transition depression and interesting electronic properties. The presented ability to produce large-scale 2D crystals with high environmental stability was applied to highly sensitive and fast optoelectronic sensors. This intercalation-based approach extends the morphological, compositional, and thermodynamic complexity of 2D materials. Second, the interaction of intercalants with 2D materials junctions was shown to produce a novel selective chemical stabilization effects. The preferential interaction of fluorine with a functionalized graphene layer was shown to provide a unique and virtually perfect etch selectivity of graphene layers in a plasma. The atomic thickness and unprecedented etch stability of 2D materials junctions was applied to ultra-high-resolution fabrication of semiconductors through a facile offset pattering approach yielding atomically-precise nanostructures at large scale for future electronics. Finally, I will demonstrate the 2D material-enabled modification of intercalants and their unique applications to electronics. By nanoelectromechanical confinement of intercalated water between two graphene layers, a 2D ice phase could be formed at room temperature that exhibits a strong and permanent dipole. Our observation represents the first direct
observation of ferroelectric properties of water ice in a 2D phase. Characterization of this permanent polarization with respect to varying water partial pressure and temperature reveals the importance of forming a monolayer of 2D ice for ferroelectric ordering which agrees with theoretical modeling . The observed robust ferroelectric properties of 2D ice enable novel nanoelectromechanical devices that exhibit memristive properties. A unique bipolar mechanical switching behavior was observed where previous charging history controls the transition voltage between low-resistance and high-resistance state. This advance enables the realization of rugged, non-volatile, mechanical memory exhibiting switching ratios of 106, 4bit storage capabilities and no degradation after 10,000 switching cycles.
1. S.H. Chen et al. Adv. Funct. Mater. (2020) DOI: 10.1002/adfm.202004370
2. Chin, HT. et al. npj 2D Mater Appl (2021) DOI: 10.1038/s41699-021-00207-2

Optically-active defects in crystals can serve on-demand single photons and coherent spin qubits. Therefore, they provide important hardware for solid-state quantum architectures. However, limitation in optical interface and unwanted interaction in solid-state environment prevents efficient control and readout of the qubits states. Here, we present recent progress for high-resolution and high contrast optical interfaces for defect qubits as well as suppressed phonon interaction in point-planar defect complex in nanowire structures. Our approaches enable us to address defects with higher resolution and sensitivity, and therefore it will pave a new way of exploring solid-state quantum systems.

A particularly interesting application of diamond based quantum sensing is the detection of nuclear magnetic resonance on nanometer scales, including the detection of individual nuclear spins or small ensembles of external nuclear spins. Single nitrogen vacancy (NV) color centers in diamond currently have sufficient sensitivity for detecting single external nuclear spins and resolve their position within a few angstroms. The ability to bring the sensor close to biomolecules by implantation of single NV centers and attachment of proteins to the surface of diamond enabled the first proof of principle demonstration of proteins labeled by paramagnetic markers and label-free detection of the signal from a single protein. Single-molecule nuclear magnetic resonance (NMR) experiments open the way towards unraveling dynamics and structure of single biomolecules. However, for that purpose, NV magnetometers must reach spectral resolutions comparable to that of conventional solution state NMR. New techniques for this purpose will be discussed. Most of mentioned above results obtained so far with diamond centers are based on optical detection of single NV color centers. We will also show how photoelectrical detection of NV centers base on spin selective photoionization can provide robust and efficient access to spin state of individual color center.

Wavelength-selective thermal emitters, which produce only light in a specific wavelength range when heated, can improve the energy utilization
efficiency in various thermal radiation applications such as spectroscopic analysis, illumination, heating, and energy conversion. By appropriately
designing both the optical absorption spectra of the materials of emitters and the optical resonance spectra of the structures of the emitters, we have
realized wavelength-selective thermal emitters operating at various wavelengths ranging from mid-infrared to near-infrared and visible. In this presentation, we introduce narrow-band thermal emitters in the midinfrared region and their fast modulation. We also introduce wavelengthselective thermal emitters in the near-infrared region and their application to thermophotovoltaic power generation systems.

The demand for miniaturizing optical devices is growing as it becomes a critical factor to determine the design and performance of mobile and wearable platforms like smartphones and smartwatches. Metasurface technology is excellent for achieving this in that it provides maximal spatial sampling rates for precisely controlling light suppressing higher-order diffractions of conventional diffractive optical elements. We will present Structured-Light (SL) projectors made of dielectric metasurface optical elements and near-infrared laser diodes. The metasurfaces are composed of amorphous Si pillars sitting on a Quartz substrate. The pillars are fabricated by photolithography and nanofabrication processes arranged with sub-wavelength intervals. The metasurface SL projectors provide simple and compact module solutions for optical 3D sensors. Only a single metasurface element constitutes the projector optics. Also, small module volumes (heights lower than 2mm) are possible. Metasurfaces can minimize various optical devices for next-generation mobile and wearable platforms with simple mass fabrication.

This lecture covers trends of metastructure designs to enhance imaging resolution. Especially, enhanced imaging resolution techniques with metastructures are introduced to understand complex biological system. Among the many approaches, dielectric metastructures in contact with the inside of cells have been reported as a one of useful imaging applications since an observation volume can be confined down to few-tens nanometre theoretically. Here, we introduce the technique to fabricate meta nanoarrays that consist of SiO2 nanopillars terminated with gold nanodisks, allowing extreme light localization. The electromagnetic field profiles of the meta-arrays are obtained through simulations and imaging resolution of cell membrane and biomolecules in living cells are tested. Moreover, we discuss the feasibility of metastructures to unveil unknown biological events under environmental extreme.

Plasmonically enhanced spectroscopies, such as the surface-enhanced Raman spectroscopy (SERS) and the tip-enhanced Raman spectroscopy (TERS) have been well utilized for both, sensing tiny amounts of specific molecules, and imaging various samples at the nanoscale. The most important phenomenon in such measurements is the selective enhancement of Raman signal from the nanometric volume of a sample, which makes it possible to study a sample at extremely high spatial resolution, or when the sample may have a very low concentration. A large amount of research has been dedicated to improve the enhancement factor in such plasmonic techniques, and it has been realized that it is very crucial to properly design the plasmonic nanoparticles to achieve desired enhancements. In order to obtain better enhancement in TERS, one needs to match three wavelengths, namely the wavelength of the incident light, the resonance Raman wavelength of the sample and the plasmon resonance wavelength of the nanotip. When the three overlap with each other, both Raman and plasmon resonances simultaneously take place at the excitation wavelength, providing maximum possible enhancement to the scattered signal. For a given sample, one can select a laser with a wavelength that matches the resonance Raman wavelength of the sample, and hence it finally comes down on designing the nanotip in such a way that the plasmon resonance wavelength of the nanotip matches precisely with the other two wavelengths. Here, we will discuss how we design a plasmonic nanotips, where one can tune the plasmon resonance wavelength within the entire visible spectrum. We will show some interesting results on plasmon tuning and optical nanoimaging with high spatial resolution. Further, for the wide-spectrum tunability, we demonstrate the creation of a white-nano-light source at the apex of a plasmonic nano-tip. This new technique enables us not only to achieve wide-range tunability in TERS, but also allows us to do a background-free measurement. We will also demonstrate the selective detection of a possible presence of pesticide molecules on food by tuning the plasmon resonance to match the resonance Raman wavelength of pesticide molecules. We will show that we were able to detect a very tiny amount of pesticide, which was not detectable by conventional techniques.

I will introduce and discuss about a new molecular computing chip, lipid nanotablet (LNT), that is based on a plasmonic nanoprobe-modified lipid bilayer. The LNT platform allows for reliably tracking and controlling the interactions between plasmonic nanoparticles in situ on a synthetic cell membrane surface. It will be shown that this LNT platform is versatile and powerful in providing a modular, scalable DNA computing platform for building a nanoparticle-based computing architecture and nanoparticle neural networks that can make autonomous logic decisions. The potential for using this LNT platform for next-generation smart biosensing applications will be also discussed.

This presentation will introduce how we have utilized a frequency comb for multi-scale high precision dimensional measurements, ranging from sub-nanometer-scale thermo-plasmonic motions to kilometer-scale inter-satellite-distances. The frequency comb of a femtosecond pulse laser provides a repetitive pulse train in the time domain and millions of evenly spaced optical laser modes in the frequency domain; these features enabled the endowment of Nobel Prize in Physics to frequency comb in 2005. Over the recent two decades, all the fields in precision metrology have benefited from this frequency comb technology; high-precision dimensional metrology was not an exception. In large scales, we reported nanometer-precision time-of-flight measurement for large-scale engineering and future space missions. In medium scales, precision stage positioning and dimensional inspection required in semiconductor and display industries were proven to get precision improvement from the frequency comb. In small scales, we reported that frequency comb can successfully maintain core performances in photon plasmon conversion by exploiting plasmonic extraordinary transmission through a subwavelength plasmonic hole array, so it can be used for high-resolution phase spectroscopy in the field of plasmonics for realizing picometer resolution plasmonic ruler. These series of demonstrations prove that the frequency comb will be the key technology to open the new vista of future precision metrology.

We demonstrate a new device architecture for flexible vertical Schottky barrier (SB) transistors and logic gates based on graphene–semiconductor–metal heterostructures and ion gel gate dielectrics. The vertical SB transistor structure was formed by (i) vertically sandwiching a semiconductor layer between graphene (source) and metal (drain) electrodes and (ii) employing a separate coplanar gate electrode bridged with the vertical channel through an ion gel. Various kinds of semiconductors such as transition mechanically-exfoliated metal dicharcogenides (MoS2 and WSe2), vacuum-deposited organic semiconductors (pentacene and PTCDI-C8), solution-processed indium-gallium-zinc-oxides, and polymer semiconductors were successfully applied as a vertical channel materials. The channel current was controlled by adjusting the SB height at the graphene/semiconductor heterojunction under application of an external gate voltage. The high intrinsic capacitance of the ion-gel gate dielectric facilitated modulation of the SB height at the source/channel heterojunction to around 0.5 eV at a gate voltage lower than 2 V. The resulting vertical SB transistors exhibited a high current density, a high on−off current ratio, and excellent operational and environmental stabilities. The simple structure of the unit transistor enables the successful fabrication of low-power logic gates based on device assemblies, such as the NOT, NAND, and NOR gates, prepared on a flexible substrate. The facile, large-area, and room-temperature deposition of both semiconductors and gate insulators integrates with transparent and flexible graphene opens up new opportunities for realizing graphene-based future electronics.

Supercapacitors (SCs) are an electrochemical energy storage device that can fill the gap between batteries and electrolytic capacitors. However, the widespread applications of commercialized carbonbased SCs are limited by their energy density, arising from their physical charge storage mechanism, which is by far lower than that of batteries. Moreover, the high-power applications of SCs are also limited by the slower kinetics than electrolytic capacitor due to the diffusion and distribution of ions onto the tortuous porous surface.
In this talk, I will introduce our recent progress on the rational design of 2D pseudocapacitive materials for high energy- and high power-oriented SCs applications. Firstly, I will address our contribution to the improvement of pseudocapacitance by the molecular level surface redox sites of 2D pseudocapacitive nanomaterials such as P-doped graphene and black phosphorus. In addition to energy aspect, we will focus on the kinetics feature of 2D MXenes, correlating with the multiscale structure and chemistry for ultrahigh power and high frequency response.

Chiral structure controlled at nanoscale provides a new route to achieve intriguing optical properties such as polarization control and negative refractive index. However, asymmetric structure control with nanometer precision is difficult to accomplish due to limited resolution and complex processes of conventional methods. Here, we demonstrated novel chiral gold nanostructures exploiting chirality transfer between peptide and high-Miller-index gold surfaces. Enantioselective adsorption of peptides results in unequal development of nanoparticle surface and this asymmetric evolution leads to highly twisted chiral element in single nanoparticle making unprecedented 432 helicoid morphology. The synthesized helicoid nanoparticle showed strong optical activity which was substantiated by distinct transmittance color change of helicoid solution under polarized light.

We will present new approaches to design and fabricate resonant nano-cavities and manipulate plasmons and phonon-polaritons. First, we will present experimental results on plasmon-phonon ultrastrong coupling in epsilon-near-zero coaxial ring cavities. Next, we will describe a new device structure – ‘image polariton’ resonator – that can be coupled with graphene, boron nitride, or other 2D materials to probe ultraconfined polaritons with high coupling efficiency. Potential applications of these engineered nanocavities include infrared sensing, molecular fingerprinting, photodetection, nonlinear optics, and on-chip waveguide integration.

Photoanodes that are effective in oxidizing water under visible light play an important role in construction of artificial photosynthesis systems such as overall water splitting, N2 fixation systems and so on.
In particular, gold nanoparticles (Au-NPs) loaded on titanium dioxide (TiO2) semiconductor system has been attracting much attention because it can absorb visible light due to localized surface plasmon resonance (LSPR) of Au-NPs. Such plasmonic Au-NPs not only function as a light-absorbing unit but also promote plasmon-induced hot carriers generation, and the charge separation of those hot carriers takes place at the Au-NPs/TiO2 interface, followed by reduction/oxidation reactions. However, the LSPR of a monolayer Au-NPs on a TiO2 substrate cannot achieve sufficient and broad-band light absorption, and the quantum yield of water oxidation reaction is still low.
Recently, we have developed a novel photoanode that utilized strong coupling between LSPR and Fabry–Pérot (FP) nanocavity to solve the issues of plasmonic water oxidation. In addition to increasing the absorption efficiency and broadening the absorption wavelength range, we also succeeded in improving the quantum yield of water oxidation reaction. The structure of the photoanode that exhibits strong coupling consists of Au-NPs/TiO2 thin film/Au-film (ATA). A component of the photoanode, TiO2 thin film/Au-film, act as a FP nanocavity. Strong coupling is induced when the resonant wavelengths of the nanocavity and the LSPR of Au-NPs match each other closely.
In my talk, the coupling strength of strong coupling system that depends on the number of Au-NPs per unit area will be introduced. In addition, using Au/Ag alloy NPs as a plasmonic component in the strong coupling photoanode to increase the coupling strength and the water oxidation reaction efficiency will also be talked.

Chirality is ubiquitous in nature and is hard-wired into every living biological system. The well-known examples are L-type amino acids and D-type nucleic acids and glycans. Since the chirality of building blocks decides the handedness of assembled structures, proteins such as enzymes and receptors are also chiral. Importantly, their chiral structures are closely related to their biological properties. For example, depending on the chirality of molecules that are consumed or reach the taste buds or olfactory receptors, they taste sweet or bitter, and smell differently. These chiral-sensitive receptors are not just limited to the tongue or nose, but distributed in the stomach, intestine, and pancreas that govern overall physiology. Likewise, chirality is an important architectural consideration to build an effective artificial enzyme. There have been enormous efforts to mimic enzymatic functionalities by developing artificial structures to utilize them under relatively harsher conditions than that in the body. However, due to the limited stability and the lack of high selectivity, it has still remained challenging. Using inorganic materials is a powerful strategy to solve these problems. Due to the thick electron clouds, inorganic materials show high catalytic activity, sensitivity, and stronger interactions with electric, electromagnetic and magnetic fields that amplify the signal. Thus, nanostructures designed with inorganic materials and biomimetic properties will offer efficient signal transition/ amplification, higher chemical and physical tolerance, and multi-functionality. In the talk, I will convey how chiral engineering using inorganic nanostructures will provide “smart” platforms, a new level of control for drug delivery systems, tumor detection markers, biosensors, and other biomaterial based devices.

The field of chirality has seen a strong rejuvenation due to the observation of nanoscale chirality in plasmonic nanoparticles. This lecture will highlight recent advances in the field of plasmonic chirality, including novel methods for the synthesis of optically active plasmonic nanomaterials. The focus will be first directed toward the directed self-assembly of gold nanorods into chiral nanostructures, using amyloid fibers as templates, as well as potential application for such nanomaterials in the diagnosis of neurodegenerative disorders. We will also introduce the chiral synthesis of colloidal nanoparticles with chiral morphology. The self-organization of surfactant micelles on nanoparticle seeds offers a wide range of possibilities, which have been studied in the context of the seeded growth of metal nanoparticles. Through the addition of chiral co-surfactants, quasi-helical micelles are obtained, which wrap around gold nanocrystals and template seeded growth into chiral features. The resulting chiral nanoparticle colloids display optical handedness, which can be tuned through the visible and the near IR. This approach thus provides an appealing method toward the fabrication of nanoparticles with high chiral optical activity.

To achieve a high solar-to-hydrogen (STH) conversion efficiency, strategies towards high photocurrent together with sufficient onset potential should be developed. Herein, we report a SnS semiconductor as a high-performance photocathode. Utilizing a sulfur precursor with a weak dipole moment generates high-quality dense SnS nanoplates with enlarged favorable crystallographic facets and suppress anisotropic growth. Furthermore, the introducing Ga2O3 layer between SnS and TiO2 in SnS photocathodes efficiently improves the charge transport kinetics without charge trapping. The SnS photocathode reveals the highest photocurrent density of 28 mA cm−2 at 0 V versus the reversible hydrogen electrode. In this study, for the first time, we demonstrated overall solar water splitting by combining an optimized SnS photocathode with a Mo:BiVO4 photoanode, achieving a STH efficiency of 1.7% and long-term stability of 24 h. The high-performance and low-cost SnS photocathode represents a promising new material in the field of photoelectrochemical solar water splitting. Solar water splitting directly converts solar energy into H2 fuel that is suitable for storage and transport. We further develop elaborate strategies yielding a high photocurrent in a tandem configuration along with sufficient photovoltage. Highly efficient solar water splitting devices based on emerging low-cost Sb2Se3 photocathodes coupled with semitransparent perovskite photovoltaics were demonstrated. A state-of-the-art Sb2Se3 photocathode exhibiting efficient long-wavelength photon harvesting enabled by judicious selection of junction layers was employed as a bottom absorber component. The top semitransparent photovoltaic cells, i.e., parallelized nanopillar perovskites using an anodized aluminum oxide scaffold, allowed the transmittance, photocurrent, and photovoltage to be precisely adjusted by changing the filling level of the perovskite layer in the scaffold. The optimum tandem device, in which similar current values were allocated to the top and bottom cells, achieved an STH conversion efficiency exceeding 10% by efficiently utilizing a broad range of photons at wavelength over 1000 nm.

Decrease in processing speed due to increased resistance and capacitance delay is a major obstacle for the down-scaling of interconnects. In this talk, we will introduce 3nm thick amorphous boron nitride (a-BN) films with ultralow-κ (ULK) values of 1.78 at operation frequencies of 100 kHz without pore. The films are mechanically and electrically robust, with a breakdown strength of 7.3 MV/cm, which exceeds requirements. Cross-sectional
imaging reveals that amorphous boron nitride prevents the diffusion of cobalt atoms into silicon under very harsh conditions, in contrast to reference barriers. In addition, we will discuss the past, present, and future of ULK.

An acoustic graphene plasmon (AGP) supported by a heterostructure comprising of a metal, a thin dielectric spacer, and a graphene layer is mostly confined in the dielectric and does not exhibit a cutoff when spacer thickness reduces to a ~1 nm scale. Therefore, AGP provides an unexcelled mode volume confinement factor up to ~1010, outperforming all known polaritonic modes in 2D materials. So far, AGP probing has been demonstrated either in the far-field regime in mid-IR, or via the near-field-mediated photocurrent measurements at THz frequencies.

We report on the first near-field optical imaging of AGP, employing a scattering-type scanning near-field optical microscope (s-SNOM) in the mid-IR. We directly measure the AGP dispersion and propagation loss, and investigate its behavior in a periodic structure. Most importantly, our results reveal a small damping rate of infrared AGP even when unprotected large-area CVD graphene is used at ambient conditions. The probed AGP mode is up to 2.3 times more compressed, yet exhibits a 1.4 times lower damping rate than the graphene surface plasmon under similar conditions. Our results highlight the importance of AGP as a superior plasmonic species as compared to the graphene surface plasmons, and suggest exceptionally promising prospects for creation of large-area graphene-based optoelectronic devices operating in the mid-IR.

The vacuum tube was the basic electronic component, which made possible new enormous invention such as radio, television, and telephone in the 1940s. The first electronic digital computer, ENIAC was based on this vacuum tube. However, the breakthrough came from the invention of the transistor, which opened the new era of solid-state microelectronics by destructing the previous vacuum tube industry. Even if the transistor was a huge revolution from the previous technology of vacuum tube, this off-chip transistor production was also replaced by the planar type of modern transistor which was evolved as integrated circuits (IC) invented by Jack Kilby and Robert Noyce in 1958/1959. In the solid-state microelectronics history during > 70 years, new products have literally been killing off older products in a process of creative destruction, which is famous concept of Joseph Schumpeter. It means the 2D patterning technology has gradually scaled down to meet the profitably industrial production together with the diameter increase of thin-slice semiconductor wafer size over half century. However, the planar scaling according to Moore’s law retards and faces the physical dimension limitation with the exponential cost increase. In an economical viewpoint, some chipmakers already announced no more investment on the conventional pitch scaling competition. In other words, it is time to start reconsidering the gaming rule not toward 2D shrinkage but 3D compact integration. The vertical device architecture should be most effectively achieved by advanced semiconductor packaging technology. The major candidates as new semiconductor nanofabrication process can be presented and discussed to lead a future semiconductor platform technology

Recently, huge demand for the next generation communication has led a megatrend to increase the operating frequency of radio frequency (RF) devices and integrate several functions in a single chip. Recent studies have provided analog-digital mixed-signal system on chip (SoC) based on Si CMOS and advanced packaging technology, but these approaches have several technical challenges. As the Si CMOS technology confronts its scaling limit, it is quite challenging to further improve the RF performance of Si CMOS. Also, a complex design and process are essential to reduce substrate coupled digital noise. Furthermore, the packaging technology has a fundamental drawback of the long interconnect, high loss, and high power consumption. To overcome the limitation of conventional mixed-signal systems, an M3D integrated mixed-signal system is emerging as one of the strongest potential solution. Therefore, in this study, we propose and discuss the InGaAs HEMTs on Si CMOS for the substrate coupling noise-free M3D mixed-signal IC.

As the critical backbone material of recent information technology, silicon is extensively used as a structural material in micro- and nano-systems. Although many research studies have reported superior elastic strain in silicon nanostructures such as nanowires, nanomembranes, and nanoribbons, the fabrication techniques on the silicon nanostructures and their related mechanical properties are not fully understood.
In this lecture, whole wafer-scale uniform nano-scale silicon posts using a conventional microfabrication process will be demonstrated. A combined fabrication technique of DRIE and size-reduced RIE could control the sub-micron and nanometer post dimensions. Unlike using the expensive e-beam lithography, this fabrication technique provided cost-effectiveness because a conventional photomask with a minimum feature size of 2.0 μm was used for whole wafer-scale photolithography. Furthermore, we will discuss the measurement method to gain the elastic deformation of the fabricated structures. In-situ nanomechanical tests of the fabricated silicon posts were processed using a pico-indenter monitored under scanning electron microscopy. Also, some measurement issues with this pico-indenter measurement and some suggesting solutions will be addressed. Finally, I will provide potential applications of these nanometer silicon posts for applying to the MEMS-based ultrasonic transducers from the measurement results.

Display can be developed as a trend of maximizing realism, diversifying the use environment, and converging with various functions. In order to maximize the sense of realism, efforts to improve image quality such as resolution, color reproduction capability, and contrast ratio of flat panel displays, as well as technology development for space displays which can express three-dimensional images, are steadily progressing. As AR/VR and Metaverse services attract much attentions, high resolution panels to show high quality or 3D images with small form factor are getting more important.
Organic light-emitting diode(OLED) microdisplays have attracted much attention due to self-emission property which can lead to small form factor devices as well as good image quality. In ETRI, we have developed 1280x1034 (SXGA) and 1920x540 (32:9 ratio) resolution OLED microdisplays with the sub pixel size of 3.4 or 3.6 micrometer. The small form factor display can be applied to glass like AR devices. Moreover, 1 micrometer pixel pitch spatial light modulator has been developed, which was applied to digital holography. The micrometer pixel panel could result in a wider field of view (~30 degree) digital hologram than ever before. In this presentation the detailed results on micrometer pixel displays for digital reality will be discussed.

Organic and hybrid electronics have shown great potentials in applications including large area imager, thin film circuits, and displays in the past few decades. To bring the technology level of organic electronics to a market acceptable status, it is very important to integrate the organic electronics in an industrial compatible process flow. Photolithography is a well-known method to create high resolution patterns with high throughput in semiconductor industry. In this presentation, we will present our OTFT developments for thin film circuits applications, such as microprocessor and RFID. We will also present the latest development in imager for fingerprint sensor applications. Furthermore, we will show our developments in patterning organic semiconductors for OLED applications to realize high resolution OLED pixels side-by-side with high aperture ratio for the future mobile and AR/VR display.

With decreasing feature sizes along “Moore’s law” and the associated increase in power density,[1] heat dissipation is arguably the most important problem facing electronic chips today. The thermal conduction within a chip comprises multi-stage challenges from devices into the substrate. The propagation is further impeded by transistors and neighboring interconnects as principles break down at the length scale. To tackle such thermal challenges, for decades, a significant effort has been made from nanoscale thermal characterization to engineering fabrication process. This presentation comprises into three parts: a direct quantification of heat generation due to incident of high energy electrons, thermal transport in nanomaterials, and our approaches to improve thermal transport in an atomic film.

First, I will discuss the origin of heat generation due to electron conduction.[2] To directly capture the heat generation, we specifically design and develop a nanowatt calorimeter, compatible with a transmission electron microscopy. In combination of the calorimeter and electron energy loss spectroscopy, we unveil the origin of heat generation show that the characteristic length scale contributing to heat generation is longer than those for the other inelastic phenomena. The second part of this talk will discuss quasi-ballistic phonon transport in nanostructured materials. I also discuss the modification of phonon transport characteristics from Brownian motion to Levy walk due to increased boundary scattering with large axial angles. The last part will introduce an approach to improve electronic and thermal properties of atomic thin films with the modulation of plasma treatment. In this work, a substrate bias during plasma exposure serves as a temporally selective heat treatment during atomic layer deposition, extending a processing temperature.[3]

References
[1] I. Ferain, C. A. Colinge, J.-P. Colinge, Nature 2011,479, 310.
[2] J. Park, K. Bae, T. R. Kim, C. Perez, A. Sood, M. Asheghi, K. E. Goodson, W. Park, Advanced Science 2021,8, 2002876.
[3] Y. Kim, H. Kwon, H. S. Han, H. J. K. Kim, B. S. Kim, B. C. Lee, J. Lee, M. Asheghi, F. B. Prinz, K. E. Goodson, ACS Applied Materials & Interfaces 2020,12, 44912.

Graphene is a nanomaterial in which carbon atoms are arranged in hexagonal structures, which is recognized as the best novel material among existing materials for its high strength and electron mobility, and competition for technology development is fierce around the world wide. Therefore, graphene can be applied to the diverse industries such as transparent flexible display, airplane, battery, semiconductor, and an ultra-light car; however, safety evaluation data on graphene is currently limited. Here, we performed general toxicity studies of reduced graphene oxide including a single and 4-week repeated dose toxicity test in Sprague-Dawley rats, and a skin sensitization test in guinea pigs following the Organization for Economic Cooperation and Development (OECD) test guidelines 406 and 407 in addition to Good Laboratory Practice.
To investigate the NOAEL and target organs of reduced graphene oxide, Sprague-Dawley rats were allocated to 4 groups: vehicle control (0.5% BSA solution), 35 mg/kg, 70 mg/kg, 140 mg/kg dose test groups and reduced graphene oxide was administered over 4 weeks after single dose in rats based on the results of the single oral administration toxicity study in rats. The results of the study showed that the NOAEL of reduced graphene oxide was 140 mg/kg for both sexes of rats without adverse effects in a 4-week repeated oral toxicity study and there was no skin hypersensitivity reaction in guinea pigs. Therefore, our results reveal the potential for safe application of graphene to various industries.

Understanding the interactions between nanoparticles (NPs) and human immune cells is necessary for justifying their utilization in consumer products and biomedical applications. However, conventional assays may be insufficient in describing the complexity and heterogeneity of cell–NP interactions. Herein, mass cytometry and single-cell RNA-sequencing (scRNA-seq) are complementarily used to investigate the heterogeneous interactions between silver nanoparticles (AgNPs) and primary immune cells. Mass cytometry reveals the heterogeneous biodistribution of the positively charged polyethylenimine-coated AgNPs in various cell types and finds that monocytes and B cells have higher association with the AgNPs than other populations. scRNA-seq data of these two cell types demonstrate that each type has distinct responses to AgNP treatment: NRF2-mediated oxidative stress is confined to B cells, whereas monocytes show Fcγ-mediated phagocytosis. Besides the between-population heterogeneity, analysis of single-cell dose–response relationships further reveals within-population diversity for the B cells and naïve CD4+ T cells. Distinct subsets having different levels of cellular responses with respect to their cellular AgNP doses are found. This study demonstrates that the complementary use of mass cytometry and scRNA-seq is helpful for gaining in-depth knowledge on the heterogeneous interactions between immune cells and NPs and can be incorporated into future toxicity assessments of nanomaterials

Nanomaterial development and research have precipitously increased recently, and engineered nano-related items are continuously introduced to the market. The use of nanomaterials extends to cosmetics, fabrics and clothing, personal care items, cleaning solutions, sporting equipment and electronics as well as toys for children; however, there are limited information of nanomaterials about the potential adverse effects in human health. In particular, potential adverse health effects of nanomaterials in developmental and reproductive function has been relatively less investigated in the nanotoxicology area. In this presentation, I will introduce the general overview of developmental and reproductive toxicities of nanomaterials and our toxicology study results with nanomaterials, including titanium dioxide, cerium oxide, zinc oxide, and silicon dioxide nanoparticles.

In our previous study, we found that 20 nm-silica nanoparticles (SiNPs), but not 50 nm-SiNPs, induced an inflammatory response the lung of mice instilled repeatedly via the trachea for 90 days. To clarify the size-dependent response, we here compared the toxic mechanism of both sizes of SiNPs in vitro and in vivo. Cell viability decreased in cells exposed to both sizes of SiNPs compared with controls. The 20 nm- and 50 nm-SiNPs formed giant and autolysosome-like vacuoles in the cytosol, respectively, and structural damage of organelles, such as mitochondria, the endoplasmic reticulum (ER), lysosomes, and cell membranes, was more pronounced in cells exposed to 20 nm-SiNPs than in those exposed to 50 nm-SiNPs. While intracellular levels of reactive oxygen species were higher in cells exposed to both sizes of SiNPs compared with controls, intracellular calcium ions accumulated only in cells exposed to the smaller SiNPs. The total number of cells and the relative proportion of neutrophils were clearly elevated in the lungs of all mice exposed to 20 nm- and 50 nm-SiNPs compared with those in controls. Meanwhile, the levels of interleukin-6, macrophage inflammatory protein-1 alpha and monocyte chemoattractant protein-1 alpha significantly elevated only in the lungs of mice exposed to 20 nm-SiNPs. We also found that both sizes of SiNPs inhibited differentiation into M1 and M2 macrophages and decreased expression of adhesion molecules. Given that accumulation of giant vacuoles and dilation of the ER and mitochondria are key indicators of paraptosis, we suggest that 20 nm-SiNPs induce paraptosis-like cell death, leading to an inflammatory response.

EU REACH is the strictest law to govern the registration, evaluation, authorization and restriction of substances made available on the EU market. Although the scope of the REACH regulation doesn’t express the reference to nanomaterials, nanomaterials are covered by the definition of ‘substance’. It means only nanomaterials which have been registered according to REACH regulation can be manufactured and placed on the EU market. As of 1 January 2020, explicit legal requirements under REACH apply for companies that manufacture or import nanoforms after lengthy discussions. These reporting obligations address specific information requirements, outlined in revised annexes to the REACH regulation. It is very difficult to define nanomaterials, but nanomaterials are defined as the physical size, the shape and the volume specific surface areas under K-REACH on the aspect of regulation for chemical risk assessment, even though nanomaterials have diverse definitions scientifically. Under K-REACH nanomaterials, which is manufactured or imported over 1000 ton per year should be registered by 2024. But potential registrants are suffered to prepare registration dossier and physicochemical properties because of the lack of recognition on nanomaterials. The objectives of this presentation will show the current status of preparing nanomaterials registration as followings; First, the nomenclature and requirements for substance identification regarding nanomaterials will be compared under REACH and K-REACH. Second, the current status of manufacturing and importing of nanomaterials in Korea will be showed to register according to deadline of K-REACH. Third, the supporting activities by governmental level are introduced for K-REACH compliance to industries.

Plastic waste has been growing issue in environment and public health. There are various plastic depending on the chemical structure such as polyethylene (PE), polypropylene (PP), polystyrene (PS). Among them, PS nanoplastics were mainly used for risk assessment due to its commercial availability. However, PP is widely used plastics for packaging and mask and their risk assessment is rarely investigated due to the lack of reference materials. In this talk, I will present the synthetic methods of PP nano- and microplastics as reference materials and demonstrated their bioaccumulation study using zebrafish embryos. PP nanoplastics were prepared the modified non-solvent induced phase separation and fluorescently labeled by combined swelling-diffusion method. Their size was from hundreds nanometer to tens micrometer with spherical and fragmented shape. The red-fluorescent labeled nanoplastics were treated in zebrafish embroys for bioaccumulation study and found in mainly intestinal region of developing zebrafish with low mortality.