- Development of a ‘Nanomachines’ that penetrates and kills cells via mechanical molecular movements - Selective penetration of cancer cells using a latch molecule released near cancer cells Proteins are involved in every biological process, and use the energy in the body to alter their structure via mechanical movements. They are considered biological 'nanomachines' because the smallest structural change in a protein has a significant effect on biological processes. The development of nanomachines that mimic proteins has received much attention to implement movement in the cellular environment. However, there are various mechanisms by which cells attempt to protect themselves from the action of these nanomachines. This limits the realization of any relevant mechanical movement of nanomachines that could be applied for medical purposes. The research team led by Dr. Youngdo Jeong from the Center for Advanced Biomolecular Recognition at the Korea Institute of Science and Technology (KIST, President Seok-Jin Yoon) has reported the development of a novel biochemical nanomachine that penetrates the cell membrane and kills the cell via the molecular movements of folding and unfolding in specific cellular environments, such as cancer cells, as a result of a collaboration with the teams of Prof. Sang Kyu Kwak from the School of Energy and Chemical Engineering and Prof. Ja-Hyoung Ryu from the Department of Chemistry at the Ulsan National Institute of Science and Technology (UNIST, President Yong Hoon Lee), and Dr. Chaekyu Kim of Fusion Biotechnology, Inc. The joint research team focused on the hierarchical structure of proteins, in which the axis of the large structure and the mobile units are hierarchically separated. Therefore, only specific parts can move around the axis. Most existing nanomachines have been designed so that the mobile components and axis of the large structure are present on the same layer. Thus, these components undergo simultaneous movement, which complicates the desired control of a specific part. A hierarchical nanomachine was fabricated by synthesizing and combining 2 nm-diameter gold nanoparticles with molecules that can be folded and unfolded based on the surrounding environment. This nanomachine was comprised of mobile organic molecules and inorganic nanoparticles to function as large axis structures, and defined movement and direction in such a manner that upon reaching the cell membrane, it resulted in a mechanical folding/unfolding movement that led to the nanomachine directly penetrating the cell, destroying the organelles, and inducing apoptosis. This new method directly kills cancer cells via mechanical movements without anticancer medication, in contrast to the capsule-type nanocarriers that deliver therapeutic drugs. Subsequently, a latch molecule was threaded onto the nanomachine to control the mechanical movement to selectively kill cancer cells. The threaded latch molecule was designed to be released only in a low pH environment. Therefore, in normal cells with a relatively high pH (approximately 7.4), the movements of nanomachine was restricted and they could not penetrate the cell. However, at the low pH environment around cancer cells (approximately 6.8), the latch molecules were untied, inducing mechanical movement and cell penetration. Dr. Jeong said, “The developed nanomachine was inspired by proteins that perform biological functions by changing their shape based on their environment. We propose a novel method of directly penetrating cancer cells to kill them via the mechanical movements of molecules attached to nanomachines without drugs. This could be a new alternative to overcome the side effects of existing chemotherapy.” Image Nanomachine, developed by KIST-UNIST joint research team, which selectively penetrates and kills cancer cells, and its mechanism of action The nanomachine directly penetrates cancer cells and kills them by destroying their organelles via mechanical movements of the molecule.

- Identification of the operating mechanism of cobalt-based single-atomic catalyst and development of a mass production process - Utilization for catalyst development in various fields including fuel cells, water electrolysis, solar cells, and petrochemical Fuel cell electric vehicles (FCEVs) are an eco-friendly means of transportation that will replace internal combustion locomotives. FCEVs offer several advantages such as short charging time and long mileage. However, the excessive cost of platinum used as a fuel cell catalyst leads to limited supply of FCEVs. There has been extensive research on non-precious metal catalysts such as iron and cobalt to replace platinum; however, it is still challenging to find substitutes for platinum due to low performance and low stability of non-precious metal catalysts. The research team led by Dr. Sung Jong Yoo of the Hydrogen·Fuel Cell Research Center at Korea Institute of Science and Technology (KIST, President Seok Jin Yoon) conducted joint research with professor Jinsoo Kim of Kyung Hee University and professor Hyung-Kyu Lim of Kangwon National University; they announced that they have developed a single atomic cobalt-based catalyst with approximately 40% improved performance and stability compared to contemporary cobalt nanoparticle catalysts. Conventional catalysts are typically synthesized via pyrolysis, wherein transition metal precursors and carbon are mixed at 700？1000℃. However, due to metal aggregation and a low specific surface area, the catalysts obtained through this process had a limited activity. Accordingly, researchers have focused on synthesizing single-atomic catalysts; however, previously reported single-atomic catalysts can only be produced in small quantities because the chemical substances and synthesis methods used varied depending on the type of the synthesized catalyst . Therefore, research has focused on performance improvement of the catalyst rather than the manufacturing process. To address this problem, the spray pyrolysis method was implemented using an industrial humidifier. Droplet-shaped particles were obtained by rapidly heat-treating the droplets obtained from a humidifier. This can enable mass production through a continuous process, and any metals can be easily produced into particles. The materials used for the synthesis of metal particles should be water-soluble because the particles are made through an industrial humidifier. It was confirmed that the cobalt-based single-atomic catalysts developed through this process exhibit excellent stability as well as fuel cell performance and are 40% superior compared to conventional cobalt catalysts. Cobalt-based catalysts also cause side reactions in fuel cells; however, computational science has shown that catalysts manufactured via spray pyrolysis lead to forward reactions in fuel cells. Dr. Yoo clarified, “Through this research, a process that can enable considerable improvement in the mass production of cobalt-based single-atomic catalysts has been developed, and the operating mechanism of cobalt-based catalysts has been elucidated via close analyses and computational science. These results are expected to serve as indicators for future research on cobalt catalysts.” They also added, “We plan to expand the scope of future research to explore not only catalysts for fuel cells, but also environmental catalysts, water electrolysis, and battery fields.” Image (a) single-atomic catalyst synthesis process using humidifier method, (b) SEM image, (c) cobalt element mapping image, (d) high-resolution STEM image of cobalt single-atomic catalyst (Left) Catalyst performance reduction rate and metal dissolution rate after 100-h evaluation; (right) comparison with existing literature of cobalt- and iron-based catalysts

- First proof of information preservation relation in quantum measurement - Expected to be used for optimally designing quantum computing and quantum cryptography protocols with quantum measurements ‘Schr？dinger’s cat’ is a thought experiment designed to explain ‘quantum superposition’ and ‘quantum measurement,’ which are the core characteristics of quantum physics. In this experiment, the cat inside the box can be both alive and dead at the same time (quantum superposition), and its state (dead or alive) is decided the moment the box is opened (measured). Such quantum superposition and measurement are not only the foundation of quantum physics, but also guarantee the safety of quantum computing and cryptography. The research team, comprising Drs. Seongjin Hong, Hyang-Tag Lim, and Seung-Woo Lee from the Center for Quantum Information at the Korea Institute of Science and Technology (KIST, President Seok Jin Yoon), derived and verified the information preservation relation for the first time in quantum measurement. This strengthens the security of quantum information technologies even in weak quantum measurement realm. Opening the box (quantum measurement) accommodating the cat to obtain information on whether it is dead or alive changes the initial condition of the cat being both dead and alive at the same time (quantum superposition) to just being either dead or alive. In other words, the cat is dead from the moment we obtain the information of its ‘being dead,’ or is alive the moment we obtain the information of its ‘being alive.’ Due to the irreversibility of quantum measurements, the cat’s state cannot be reversed. However, what would have happened if the measurement had not been done completely, i.e., if the box had been opened a little bit only to reveal the cat’s tail? This event is called ‘weak measurement’ in quantum mechanics. In this case, complete information on the cat’s state cannot be obtained, and the cat’s state can be reverted to its initial state using measurement ‘reversal.’ Therefore, establishing a ‘relation of quantum information preservation’ by considering the amount of obtained, disturbed and reversible information has been a challenge in quantum physics and also an important task to ensure the security of quantum technology. The research team theoretically derived an information preservation relation considering the reversing probability along with the existing relations of ‘information gain’ and ‘state disturbance.’ This information preservation relation was experimentally verified using linear optical elements such as waveplates and polarizers to implement ‘weak measurement’ and ‘reversing operations’ and by applying them to a three-dimensional quantum state realized by a single photon. This information preservation relation reveals that obtaining more information on a quantum state by increasing the intensity of measurement disturbs the quantum state more. At the same time, it is also shown that the probability of reversing the disturbed state to its initial state before weak measurement becomes lower. It should be noted that if it were possible to reverse a disturbed quantum state to its initial state, then the safety of quantum cryptography may be not guaranteed. Drs. Hong and Lim, who led the experiment of this study, and Dr. Lee, who led the theory, said that “this is the result of perfectly establishing that quantum technology is secure in principle by proving that the total amount of information of a quantum state cannot be increased even through measurement”, and that they “expect this to be applied as an optimization technology for quantum computing, quantum cryptography, and quantum teleportation”. Image Quantum information preservation relation and schematic diagram of quantum states subjected to ‘weak measurement’ and ‘reverting operations’ (G: information obtained by measurement, F: information remaining in quantum state after measurement, R: probability of successful reversion) Selected as cover of Physical Review Letters

- Developed light-operated perovskite optoelectronic logic gate - Enabled all 5 basic logic operations with one optical-logic gate The demand is explosively increasing for computers that can quickly calculate and process large amounts of information recently, as artificial intelligence, self-driving cars, drones, and metaverse technologies are drawing attention as core industries of the future. However, electronic semiconductor logic gates, which serve as the brains of computers today, have limited capacities in high-speed data calculation and processing and have disadvantages in that they consume a lot of energy and generate considerable heat. Korea Institute of Science and Technology (KIST, President: Seok-Jin Yoon) and Gwangju Institute of Science and Technology (GIST, President: Ki-Seon Kim) announced that their research teams, led by Dr. Yusin Pak at the Sensor System Research Center (KIST) and Professor Gun Young Jung at the School of Materials Science and Engineering (GIST), have developed an ultra-high-speed, high-efficiency optoelectronic logic gates (OELGs) by using organic-inorganic perovskite photodiodes. The optoelectronic logic gate has high-speed and high-efficiency characteristics; it uses light as an input signal which demonstrates low energy loss physically and can operate only with light energy without electrical power supply. The research teams implemented a stacked perovskite optoelectronic logic gate. Two layers of perovskite thin films are vertically stacked like a sandwich and proved that the desired binary logic operation is possible by inputting two lights of different wavelengths and intensities. As the perovskite optoelectronic logic gate can freely change the photocurrent polarity using light, executing more than one logic gate operation result for the same input value is possible. Therefore, compared to the existing logic gate that can only perform one logical operation on one device, the newly developed one can implement all five different basic logic operations such as AND, OR, NAND, NOR, and NOT. It enables the development of optical processors with high spatial efficiency and integration, as one logic gate can function like five logic gates. Dr. Pak (KIST) said, “Perovskite optoelectronic logic gates that execute multiple logic operations in response to optical input are expected to be used for ultra-small and low-power universal optical sensor platforms in the future.” Prof. Jung (GIST) expected that “The optoelectronic logic gate developed through this research is an outcome of optical computing R&D that realizes five basic logic operations into one device, and will greatly contribute to next-generation optical communication, optical network, and healthcare R&D”. Image Three-dimensional bar charts for all the outputs (“OR”, “AND”, “NAND”, “NOR”, and “NOT”) obtained from the 64 pixels. The red and blue bars show clear bipolar spectral photoresponses of all the pixels with reference to the fiducial level of 0 nA (gray face). Conceptual image of an optical processor chip for optical computers using perovskite optoelectronic logic Gates

- Developed operando soft X-ray absorption spectroscopy based on radiation accelerator - Developed water oxidation electrode improved by more than 10 times The importance of ‘carbon neutrality’ is growing more than ever, as climate change caused by global warming threatens even the human right to live. The Republic of Korea has declared 'carbon neutrality by 2050' and is exerting efforts to reduce greenhouse gas emissions. In order to realize carbon neutrality, along with green hydrogen production that reduces the generation of carbon dioxide, CCU technology that utilizes already generated carbon dioxide is essential. In order for these two technologies to be effective in reducing greenhouse gas emissions, the energy used must be reduced by increasing the activity of water oxidation electrode which induces an electrochemical reaction. For this purpose, attempts have been made to understand the electronic structure of the surface of the catalyst while the reaction continues. However, due to the difficulty in conducting an experiment in an ultra-high vacuum (UHV) condition, it was only indirectly estimated through computational calculations. At the Korea Institute of Science and Technology (KIST, President: Seok-Jin Yoon), Dr. Hyung-Suk Oh and Dr. Woong Hee Lee from the Clean Energy Research Center and Dr. Keun Hwa Chae from the Advanced Analysis and Data Center developed an operando soft X-ray based absorption spectroscopy based on a radiation accelerator (10D XAS KIST beamline, ) for the first time in Korea. KIST announced that this research has developed a new strategy to fabricate electrode by observing and analyzing the surface electronic structure during the reaction of the water oxidation electrode applied to 'hydrogen production and conversion of carbon dioxide'. The research team found that general cobalt was reconstructed during the reaction, through measuring the electronic structure and spin states of the electrode surface by using accelerator-based soft X-ray absorption spectroscopy under the UHV condition. A method to improve the performance of the water oxidation electrode, through this discovery of the change in the electrode material. Thermodynamically, cobalt is prone to be in a tetravalent oxidation state under oxidation conditions, and its water oxidation activity is very low. It is necessary to maintain a trivalent oxidation state in order to maintain high water oxidation activity, that the process developed by the research team enables to obtain the 3.2 oxidation state and high activity. The developed electrode has a more than 1000 times larger electrochemical surface area compared to a commercial cobalt electrode, and move than 10 times improvement in hydrogen production performance when applied to an actual water electrolysis system. Dr. Oh said, “By developing an operando soft X-ray absorption spectrometry based on a radiation accelerator, we have taken one step further in understanding the properties of catalyst materials and improving their performance. This is an essential technology for the artificial photosynthesis, and is expected to be of great help in improving the performance of the water oxidation electrode, which is an important technology for green hydrogen production and electrochemical reconstruction.” Image The operando soft X-ray absorption spectroscopy based on radiation accelerator Schematic illustration of the operando soft X-ray absortion spectroscopy TEM and SEM images of the catalyst

- Improved efficiency of wireless energy transfer of ultrasonic waves by triboelectric power generation - Ultrasonic waves have applications in wireless charging of batteries underwater or in body-implanted electronic devices As population ages and with the advancements in medical technology, the number of patients using implanted electronic devices, such as artificial pacemakers and defibrillators, is increasing worldwide. Currently, the batteries of body-implanted devices are replaced by an incision surgery, which may lead to health complications. Accordingly, a new charging technique by wireless energy transfer is emerging that can also be used to charge the batteries of underwater devices, such as sensors, that are used for monitoring the conditions of submarine cables. The Korea Institute of Science and Technology (KIST, President: Seok-Jin Yoon) announced that a research team led by Dr. Hyun-Cheol Song at the Electronic Materials Research Center developed an ultrasonic wireless power transmission technology that can be applied in the above-mentioned research areas. Electromagnetic (EM) induction and magnetic resonance can be used in wireless energy transfer. EM induction is presently being used in smartphones and wireless earphones; however, its usage is limited because EM waves cannot pass through water or metal, resulting in short charging distance. In addition, this method cannot be easily used to recharge implanted medical devices as the heat generated during charging is harmful. The magnetic resonance method requires that the resonant frequencies of the magnetic field generator and transmitting device are exactly the same; moreover, a risk of interference with other wireless communication frequencies, such as Wi-Fi and Bluetooth, exists. The KIST team, therefore, adopted ultrasonic waves as an energy transmission medium, instead of EM waves or magnetic fields. Sonar, which uses ultrasound waves, is commonly used in underwater environments, and the safety of using ultrasonic waves in the human body has been guaranteed in various medical applications, such as organ or fetal condition diagnosis. However, the existing acoustic energy transfer methods are not commercialized easily due to the low transmission efficiency of acoustic energy. The research team developed a model that receives and converts ultrasonic waves into electrical energy using the triboelectric principle that allows for the conversion of small mechanical vibrations into electrical energy effectively. By adding a ferroelectric material to the triboelectric generator, the ultrasonic energy transfer efficiency was significantly improved from less than 1% to more than 4%. Moreover, charging of more than 8 mW power at a distance of 6 cm was possible, which was sufficient to simultaneously operate 200 LEDs or to communicate Bluetooth sensor data underwater. In addition, the newly developed device had high energy conversion efficiency and generated marginal amounts of heat. Dr. Song explained the significance of the results as follows: “This study demonstrated that electronic devices can be driven by wireless power charging via ultrasonic waves. If the stability and efficiency of the device are further improved in the future, this technology can be applied to supply power wirelessly to implantable sensors or deep-sea sensors, in which replacing batteries is cumbersome.” Image Schematic illustration of wirelessly charging a body-implanted electronic device using an ultrasonic probe Wireless acoustic energy transfer into implantable devices within pork (skin and flesh) as a substitute for the human body Underwater wireless acoustic energy transfer system that can simultaneously operate 200 LEDs and a wireless sensor in real time

- Developed an important process to secure source technology for advanced alloy material development - Developed an advanced metal hydride material in the metastable phase, suggested a growth mechanism, and published the results in Nature Similar to the widespread interest in “graphite” and “diamond,” there is growing interest in metastable phases, which have different physical properties than those of stable phases. However, processes to fabricate metastable-phase materials are highly limited. Novel findings have been published about the development of a new metastable-phase synthesis method, which can drastically improve the physical properties of various materials. A research team led by Dr. Chun, Dong Won at the Clean Energy Research Division, Korea Institute of Science and Technology (KIST; President: Yoon, Seok Jin), announced that they successfully developed a new advanced metastable-phase palladium hydride (PdHx) material. Furthermore, they identified its growth mechanism and published it in the latest issue of Nature (IF 49.962), one of the world’s most authoritative journals in science and technology. A metastable-phase material has more thermodynamic energy than that in the stable phase but requires substantial energy to attain the stable phase, unlike most other materials, which exist in the stable phase with low thermodynamic energy. The research team directly synthesized a metal hydride by growing a material that can store hydrogen under a suitable hydrogen atmosphere, without dispersing hydrogen within a metal. Notably, they successfully developed a metastable-phase metal hydride with a new crystal structure. Further, they confirmed that the developed metastable-phase material had good thermal stability and twice the hydrogen storage capacity of a stable-phase material. To elucidate the theoretical basis and scientific evidence for these findings, the research team used atomic electron tomography, which reconstitutes 3D images from 2D electron microscope images for nanometer-sized crystals in a metal hydrate, for analysis. As a result, they demonstrated that the metastable phase was thermodynamically stable, identified the 3D structure of metastable-phase crystals, and suggested a new nanoparticle growth mechanism called “multi-stage crystallization.” This study holds significance as it reveals a new paradigm in metastable-phase-based material development when most research is focused on developing stable-phase materials. Dr. Chun emphasized that “These study findings provide an important process to obtain source technology in the development of advanced alloy materials containing lightweight atoms. An additional study is expected to reveal a new paradigm in the development of metastable-phase-based eco-friendly energy materials that can store hydrogen and lithium. Similar to the Czochralski (CZ) method, which is used to produce single-crystal silicon, a key material in today’s semiconductor industry, it will be a source technology with great potential that will contribute to advanced material development.” Image The percentage of metastable-phase palladium hydrides (HCP) generated depended on the palladium concentration in the palladium aqueous solution and the electron beam intensity and content of hydrogen within the metastable phase. The percentage of metastable-phase palladium hydrides (HCP) generated depended on the palladium concentration in the palladium aqueous solution and the electron beam intensity and content of hydrogen within the metastable phase Real-time analysis of the growth process of metastable palladium hydride nanoparticles within a liquid phase by transmission electron microscopy 3D atomic structure of metastable palladium hydride nanoparticles as identified by atomic electron tomography and a schematic of the metastable-phase nanoparticle growth process

- 3T-OTS device to simulate the efficient information processing method of the human brain - A green light for the development of sensor-AI combined next-generation artificial intelligence “to be used in life and safety fields” Currently, AI services spread rapidly in daily life and in all industries. These services are enabled by connecting AI centers and terminals such as mobile devices, PCs, etc. This method, however, increases the burden on the environment by consuming a lot of power not only to drive the AI ？？system but also to transmit data. In times of war or disasters, it may become useless due to the power collapse and network failures, the consequences of which may be even more serious if it is an AI service in the life and safety field. As a next-generation artificial intelligence technology that can overcome these weaknesses, low-power and high-efficiency 'in-sensor computing' technology that mimics the information processing mechanism of the human nervous system is drawing attention. The Korea Institute of Science and Technology (KIST, President Seok-Jin Yoon) announced that its team led by Dr. Suyoun Lee (Center for Neuromorphic Engineering) has succeeded in developing ‘artificial sensory neurons’ that will be the key to the practical use of in-sensor computing. Neurons refine vast external stimuli (received by sensory organs such as eyes, nose, mouth, ears, and skin) into information in the form of spikes; and therefore, play an important role in enabling the brain to quickly integrate and perform complex tasks such as cognition, learning, reasoning, prediction, and judgment with little energy. The Ovonic threshold switch (OTS) is a two-terminal switching device that maintains a high resistance state (10-100 MΩ) below the switching voltage, and exhibits a sharp decrease in resistance above the switching voltage. In a precedent study, the team developed an artificial neuron device that mimics the action of neurons (integrate-and-fire) that generates a spike signal when the input signal exceeds a specific intensity. This study, furthermore, introduces a 3-terminal Ovonic Threshold Switch (3T-OTS) device that can control the switching voltage in order to simulate the behavior of neurons and quickly find and abstract patterns among vast amounts of data input to sensory organs. By connecting a sensor to the third electrode of the 3T-OTS device, which converts external stimuli into voltage, it was possible to realize a sensory neuron device that changes the spike patterns according to the external stimuli. The research team succeeded in realizing an artificial visual neuron device that mimics the information processing method of human sensory organs, by combining a 3T-OTS and a photodiode. In addition, by connecting an artificial visual neuron device with an artificial neural network that mimics the visual center of the brain, the team could distinguish COVID-19 infections from viral pneumonia with an accuracy of about 86.5% through image learning of chest X-rays. Dr Suyoun Lee, Director of the KIST Center for Neuromorphic Engineering, said, “This artificial sensory neuron device is a platform technology that can implement various sensory neuron devices such as sight and touch, by connecting with existing sensors. It is a crucial building block for in-sensor computing technology.” He also explained the significance of the research that “will make a great contribution to solving various social problems related to life and safety, such as, developing a medical imaging diagnostic system that can diagnose simultaneously with examinations, predicting acute heart disease through time-series pattern analysis of pulse and blood pressure, and realizing extrasensory ability to detect vibrations outside the audible frequency to prevent building collapse accidents, earthquakes, tsunamis, etc.”. Image Distinguishing COVID-19 infection through image learning of chest X-rays The 3T-OTS device provides a platform for developing artificial sensory neurons, which generate spikes responding to external stimuli.

- Prospects to leverage overcoming the limitations of 'zinc-air batteries', promising next-generation batteries - Developed bifunctional electrocatalyst with staggered p-n heterojunction applying solar cell/semiconductor interface characteristics Zinc-air batteries, which produce electricity through a chemical reaction between oxygen in the atmosphere and zinc, are considered to be next-generation candidates to meet the explosive demand for electric vehicles instead of lithium-ion batteries. They theoretically meet all required characteristics for next-generation secondary batteries, such as; high energy density, low risk of explosion, eco-friendliness that does not emit pollutants, and low cost of materials (zinc and air, which can be easily obtained from nature). The Korea Institute of Science and Technology (KIST, President Seok-Jin Yoon) announced that its research team led by Dr. Joong Kee Lee (Energy Storage Research Center) developed a technology to improve the electrochemical performance of zinc-air batteries by utilizing solar energy, which is emerging as a new research and development area in the secondary battery field. The battery developed by the research team utilizes a photoactive bifunctional air-electrocatalyst with a semiconductor structure with alternating energy levels, which significantly improves the rates of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) that generate electricity. The photoactive bifunctional catalyst is a compound that accelerates chemical reactions by absorbing light energy and has a improved light absorption ability than conventional zinc-air battery catalysts. In a zinc-air battery that uses metal and air as the anode and cathode of the battery, OER and ORR must be alternately performed for electrical energy conversion of oxygen as the cathode active material. Therefore, the catalytic activity of the positive electrode current collector, made of carbon material, is an important factor in determining the energy density and overall cell efficiency of zinc-air batteries. Accordingly, the KIST research team focused on the p-n heterojunction, the basic structural unit of solar cells and semiconductors, as a measure to improve the slow catalytic activity of zinc-air batteries. The goal was to accelerate the oxygen production-reduction process by using the interface characteristics of semiconductors in which electron movement occurs. To this end, a cathode material with a heterojunction bandgap structure was synthesized, with a n-type semiconductor (graphitic carbon nitride, g-C3N4)andap-typesemiconductor(copper-doppedZIF-67(ZeoliticImidazolateFramework-67),CuZIF-67). In addition, an experiment was conducted under real-world conditions without light in order to confirm the commercial potential of the photoactive bifunctional catalyst with a p-n heterojunction structure with alternating energy levels. The prototype battery showed an energy density of 731.9 mAh gZn-1, similar to the best performance of the existing zinc-air battery. In the presence of sunlight, the energy density increased by about 7% up to 781.7 mAh gZn-1and excellent cycle performance (334 hours, 1,000 cycles), exhibiting the best performance among known catalysts. Dr. Lee said, “Utilization of solar energy is an important part not only in improving the electrochemical performance of secondary batteries but also in realizing a sustainable society. We hope that this technology will become a catalyst that stimulates the development of new convergence technologies in semiconductor physics and electrochemistry, in addition to solving the difficulties of metal-air batteries that are emerging as an alternative to lithium-ion batteries.” Image Preparation and basic characteristics of CZ. Schematic preparation and TEM images with elemental distributions in the red rectangle marked area for CZ. Durability study of photo-enhanced Zn-air batteries. Long-term galvanostatic charge-discharge profile with zoomed dark, dark-light shifting, and light regions of the CZ-based zincair battery at a current density of 2 mA cm？ 2 for up to 1000 cycles. LED screen powered by two CZ-based RZBs in series.

- Adaptation to weak stimuli and feeling pain from dangerous stimuli - Mimicking human sensations to expedite humanoid development Human skin adapts easily to a weak and prolonged stimulus, but continuous pain is induced when a strong, noxious stimulus is applied to avoid tissue damage. This feature helps our body to adapt easily to an external environment, and protects the skin from dangerous situations. The Korea Institute of Science and Technology (KIST, Institute Director: Seok-Jin Yoon) announced that the research team led by Dr. Jung Ho Yoon at the Electronic Materials Research Center and Dr. Chong-Yun Kang, the Director of the Advanced Material Technology Research Headquarters, has developed semiconductor electronic devices that easily adapt to weak stimuli and induce pain from dangerous stimuli in a manner similar to that triggered by the human skin. The KIST research team developed electronic devices capable of adjusting the strength of a bio signal transferred to the brain according to the intensity of external stimuli by adjusting the amount of silver (Ag) particles. Ag particles are easily transported by electrical stimuli. If a small amount of Ag particles is included in a material, weak conducting filaments with nano-sized line shapes are formed, and the electric circuit formed by the filaments is disconnected by heat generation like the filament of an incandescent lamp. Based on this property, a repeated externally applied, weak stimulus can be prevented from generating additional signals by reducing the amount of flowing current over time. Conversely, if a large amount of Ag particles is included in the material, an electric circuit is formed by thick, strong filaments, and is not easily disconnected even if heat is generated. Using this principle, signals are generated to induce pain continuously when a strong stimulus is applied. KIST Director Chong-Yun Kang stated that the significance of this study lies in the fact that beyond the capacity of the electronic devices to imitate pain, they can easily adapt to weak stimuli―which are harmless to the human body―to prevent pain, and induce pain when strong stimuli harmful to the human body are applied. Dr. Jung Ho Yoon expects that the developed technology will contribute considerably to the advancement of artificial skin, organs, and humanoid robots. ### This study was supported by the Next-generation Intelligent Semiconductor Technology Development Program of the National Research Foundation of Korea and the KIST Institutional Program funded by the Ministry of Science and ICT (Minister: Dr. Hyesuk Im). The research results were published in the international journal of Advanced Science (inside back cover, Adv. Sci., 9, 2103484, 2022; IF: 16.806, top 5.24% based on the Journal Citation Reports). Image