Research

“Fingertip Immersion” in Virtual Reality with Brain Activity Measurement

[POSTECH Professor Keehoon Kim’s Team Develops Multi-Finger Haptic Display that Operates Inside MRI] What if virtual reality could go beyond sight and sound—and truly let users feel the digital world at their fingertips? A research team from POSTECH has successfully measured how tactile sensations in virtual reality (VR) influence human brain activity. By combining an MRI-compatible haptic device with functional brain imaging, the researchers captured how the brain begins to perceive virtual experiences as “real” when touch is added to visual and auditory stimuli. The study was led by professor Keehoon Kim of the Department of Mechanical Engineering at POSTECH and graduate researcher Joonsub Byun, in collaboration with professors Yong-An Chung and Hyeonseok Jeong from the Catholic University of Korea, as well as Dr. Jooyeon Kim from the Korea Basic Science Institute. Their findings were published in the journal PLOS ONE. Virtual reality technologies are already widely used in healthcare, education, gaming, and training. However, one fundamental challenge has remained unresolved: objectively measuring how deeply a person is immersed in a virtual environment. Until now, immersion has largely been evaluated through subjective questionnaires asking users how realistic or engaging the experience felt. To truly determine whether the brain accepts a virtual environment as reality, researchers needed to directly observe neural responses. Functional magnetic resonance imaging (fMRI) offers a powerful way to monitor brain activity, but conventional electronic haptic devices cannot operate inside MRI systems because the strong magnetic fields are incompatible with metallic components. To overcome this limitation, the POSTECH team developed a pneumatic multi-finger haptic display powered entirely by air pressure rather than metal-based actuators. The device delivers independent tactile sensations to four fingers simultaneously while using only non-magnetic materials, allowing it to function safely inside an MRI scanner without compromising imaging quality. Using the device, the researchers compared brain activity during VR experiences with and without tactile feedback. Experiments were conducted using a 3T (3 Tesla) fMRI system, which provides high-resolution measurements of neural activity with twice the magnetic field strength of a standard clinical MRI scanner. The results revealed that when tactile sensations were added to VR experiences, brain activation extended far beyond the regions responsible for touch alone. Areas involved in motor control, attention, and cognitive processing also showed significantly stronger responses. Most notably, neural activity increased dramatically when tactile feedback was temporally synchronized precisely with visual and auditory stimuli. The findings suggest that the human brain begins to interpret virtual experiences as genuinely real when multiple sensory signals—seeing, hearing, and touching—are integrated in perfect temporal alignment. The implications of the technology extend well beyond gaming alone. In medicine, the platform could improve surgical simulation training and enable clinicians to evaluate the effectiveness of VR-based therapies for pain management, phobias, and rehabilitation through objective brain data. The technology may also contribute to remote robotic surgery, immersive educational content, and standardized neural evaluation methods for VR content. Professor Keehoon Kim explained, “To create truly immersive virtual reality experiences, tactile sensations at the fingertips play a critical role alongside visual and auditory feedback. This study is meaningful because it introduces a new platform capable of quantitatively analyzing VR experiences using brain activity data rather than relying solely on subjective questionnaires.” The research was supported by the Korean Ministry of Health and Welfare’s Health Technology R&D Project for Dental and Medical Technologies, the Ministry of Science and ICT’s Mid-Career Researcher Program and Outstanding Young Researcher Program, and POSCO Holdings. ▶️ DOI: https://doi.org/10.1371/journal.pone.0343297

Semiconductors Enter the “Multi-tasking” Era: New Device Cuts Required Components by 75% and Quadruples Processing Speed

[POSTECH develops a low-temperature heterojunction-based transistor that implements complex circuits with a single device] Less than two decades after smartphones fit into the palm of our hands, artificial intelligence is now running on devices worn on our wrists. The challenge is that while devices continue to shrink, the amount of data they must process and the number of functions they must perform are growing exponentially. A research team at POSTECH has found a promising way to address this contradiction. A team led by Professor Byoung Hun Lee of the Department of Electrical Engineering and the Department of Semiconductor Engineering at POSTECH, together with Dr. Jae Hyeon Jun of the Department of Electrical Engineering, has developed a transistor technology that enables a single semiconductor device to perform multiple circuit functions simultaneously. The new approach significantly simplifies circuit design and increases data processing speed by fourfold compared with conventional methods. The findings were published in Advanced Functional Materials, an international journal in the fields of materials science and electronic devices. One of the key challenges in the semiconductor industry is integrating more functions into smaller chips. As the number of functions increases, so do the number of circuits and transistors required. However, when adding new functions to previously fabricated semiconductor chips, back-end-of-line(BEOL1)), processing must be conducted at temperatures below 400°C to protect the existing chip structure. The research team focused on zinc oxide(ZnO) and tellurium(Te). Both materials can be fabricated as thin, uniform films at temperatures below 200°C, making them promising candidates for next-generation semiconductor materials. By combining the two, the team created a ZnO–Te heterojunction2) transistor. The device controls current flow in a highly distinctive way. Unlike conventional semiconductors, in which current generally increases as voltage rises, this device exhibits negative differential transconductance(NDT3)), in which current decreases over a certain voltage range. The team successfully realized double negative differential transconductance(D-NDT4)), in which this phenomenon occurs twice in succession within a single device. In simple terms, the technology allows a single device to handle tasks that would normally be divided among multiple devices, thereby reducing circuit complexity. The key lies in precisely controlling the overlap length between the two materials. When the overlap region is short, the current changes only once. However, as the overlap region becomes longer, both lateral and vertical currents form simultaneously within the device, generating double current peaks. Just as a current flowing in a straight line becomes capable of more complex routing when it meets a three-dimensional intersection, the device becomes capable of more complex signal processing. Using this device, the team implemented a frequency quadrupler5) that converts one input signal into four output signals. This function would typically require multiple transistors, but the new technology achieves it with a single device, reducing the number of required transistors by 75%. In actual circuit experiments, the researchers also confirmed that data processing speed increased fourfold within a single input signal cycle. “This study demonstrates the possibility of implementing complex circuit functions at the level of a single device,” said Professor Byoung Hun Lee. “We expect this technology to be widely applicable to the development of ultra-compact AI devices and three-dimensional integrated, highly-density semiconductor systems.” This research was supported by the Core Technology Development Program for the National Semiconductor Research Laboratory and the Nano-materials Technology Development Program, funded by the Ministry of Science and ICT and the National Research Foundation of Korea. ▶️ DOI: https://doi.org/10.1002/adfm.74948 1. BEOL, Back-End-Of-Line: BEOL refers to the back-end process in semiconductor manufacturing, in which metal interconnects are formed. The device developed in this study is fabricated at temperatures below 200°C, making it compatible with BEOL processes and three-dimensional integration technologies. 2. Heterojunction: A heterojunction is a device formed by combining two semiconductors with different properties. In this study, n-type ZnO and p-type Te are combined to create unique nonlinear electrical responses by utilizing their different charge transport characteristics. 3. NDT, Negative Differential Transconductance: NDT is a phenomenon in which current decreases after a certain point as gate voltage increases. Because it exhibits nonlinear behavior unlike ordinary transistors, NDT is advantageous for specialized circuit applications such as frequency multiplication and multi-valued logic. 4. D-NDT, Double Negative Differential Transconductance: D-NDT refers to the appearance of double NDT peaks in the transfer characteristics of a single device. As an input signal sequentially passes through these double peaks, the device can generate multiple output responses within a single cycle, enabling higher-order frequency conversion. 5. Frequency Quadrupler: A frequency quadrupler is a circuit or device that converts an input frequency into an output frequency four times higher. While this function generally requires multiple devices and complex circuit configurations, the present study demonstrates it using a single-stage device.

“Flawless on the Outside, Flipped Within”: Detecting Hidden Defects in 2D Dielectrics with Light

[POSTECH Professor Sunmin Ryu’s team analyzes structural inhomogeneity in large-area thin films using interferometric SHG imaging] A material may appear flawless on the surface, yet fail to function properly. The cause lies in structural defects hidden within two-dimensional thin films, which are considered key materials for next-generation semiconductor devices. Recently, a Korean research team developed an optical analysis method that can identify these invisible defects using light. A research team led by Professor Sunmin Ryu and Ph.D. candidate Yeri Lee (Department of Chemistry) at POSTECH has developed an interferometric second-harmonic generation1) (SHG) imaging approach capable of optically identifying hidden structural defects in thin films of hexagonal boron nitride2) (hBN), a promising material as a key component for next-generation semiconductor technologies. The study was published in Advanced Materials, a leading journal in materials science. From smartphones and artificial intelligence (AI) to quantum computers, two-dimensional materials are emerging as key building blocks for next-generation electronic technologies. Among them, hBN is often referred to as a “protective layer for 2D materials” due to its excellent insulating properties, which help prevent current leakage. However, when hBN is synthesized over large areas, regions known as “antiparallel domains”3) can form within the film, where the crystal orientations are reversed. Much like sailors rowing in opposite directions aboard the same boat, these internal signals can interfere with one another, potentially degrading its electrical and optical performance despite its seemingly intact appearance. Conventional analytical techniques such as transmission electron microscopy4) (TEM) and scanning tunneling microscopy5) (STM) offer highly precise observations, but they are not well suited for rapid, large-area analysis. Raman spectroscopy, while nondestructive, also has limitations in directly distinguishing antiparallel domains. To overcome these limitations, the researchers focused on second-harmonic generation (SHG) imaging. SHG is a nonlinear optical phenomenon in which light at twice the frequency of the incident light is generated when light interacts with certain materials. By introducing an external reference signal and precisely analyzing the phase difference between the two signals, the team confirmed that antiparallel domains with SHG phases differing by exactly 180 degrees are widely present, even in regions that appear to have the same orientation. In particular, by comparing ten hBN thin films grown under different conditions, the team found that variations in SHG intensity are closely associated not only to differences in crystal orientation but also to destructive interference between antiparallel domains. In other words, the attenuation of light caused by signals generated in opposite directions enables quantitative evaluation of structural inhomogeneity in the crystal. The team also established optical criteria for evaluating the crystallinity and structural uniformity of hBN by correlating SHG intensity with Raman spectroscopy data and crystal orientation dispersion. This achievement goes beyond the detection of specific defect, opening the way for rapid, systematic quality assessment of large-area two-dimensional materials. “This study demonstrates that antiparallel domains within hBN, which have long been difficult to identify directly, can be optically distinguished,” said Professor Sunmin Ryu of POSTECH. “We expect this approach to serve as an important analytical tool not only for optimizing the growth conditions of two-dimensional materials, but also for advancing next-generation electronic, optical, and quantum devices.” This work was supported by the Mid-Career Researcher Program of the National Research Foundation of Korea and the Global Research Center for Systems Chemistry. ▶️ DOI: https://doi.org/10.1002/adma.202519546 1) Second-harmonic generation (SHG): A nonlinear optical phenomenon in which light with twice the frequency of the incident light is generated when intense light interacts with a material. 2) Hexagonal boron nitride (hBN): A representative two-dimensional insulating material with a hexagonal lattice structure, widely used in electronic and optical devices. 3) Antiparallel domain: Crystal region that have the same crystal structure but opposite crystallographic orientations. 4) TEM (Transmission Electron Microscopy): An ultrahigh-resolution microscopy technique that observes the internal structure of a sample at the atomic scale by transmitting an electron beam through it. 5) STM (Scanning Tunneling Microscopy): A technique that analyzes atomic-scale surface structures by moving an extremely sharp probe close to the sample surface and measuring changes in tunneling current.

“Breaking the Ultra-Thin Dilemma”: Contact Resistance Drops 50×, On-State Current Increases 17×

[POSTECH Research Team Led by Prof. Byoung Hun Lee Overcomes Performance Limits of Ultra-Thin Semiconductors with a Novel Localized Thick-Contact Design] As semiconductor chips become increasingly thinner, the components inside chips are locked in a fierce race to achieve the ultimate ultra-thin state. However, this has presented a structural limitation: the thinner the device, the harder it is for electricity to flow. Recently, a research team at POSTECH successfully resolved this issue through a simple yet innovative approach: "thickening only the necessary parts." The research team, led by Professor Byoung Hun Lee from POSTECH’s Department of Electrical Engineering and the Department of Semiconductor Engineering, has developed a technology that dramatically lowers contact resistance by redesigning the metal-semiconductor contact structure in ultra-thin tellurium (Te) transistors. This breakthrough was recently published in ACS Nano, a prominent international journal in the field of nanotechnology. With the rapid advancement of artificial intelligence (AI) and high-performance computing, the volume of data that semiconductors must process is surging. Consequently, the time and energy loss occurring between the "logic" (which handles computations) and "memory" (which stores data) have been identified as a major bottleneck. To address this, 3D integrated structures that stack logic and memory vertically are gaining significant traction as a next-generation technology. Fabricating these structures requires devices that can operate stably even at temperatures below 400°C. Tellurium (Te) is highly regarded as a strong candidate for semiconductor channel material due to its high charge mobility, room-temperature stability, and low-temperature processability. However, its narrow band gap makes it prone to "leakage current," where current leaks even when the transistor is turned off. To minimize this, the channel must be fabricated to an ultra-thin thickness of under 5 nanometers (nm) to precisely control electron transport. The dilemma arises because when the channel becomes too thin, electron transport across the interface between the metal electrode and the semiconductor becomes severely restricted. A Schottky barrier—an energy barrier that electrons must cross between the metal and semiconductor—grows larger as the channel gets thinner. Ultimately, while researchers could reduce leakage current, doing so simultaneously increased contact resistance, significantly degrading device performance. To overcome this, the POSTECH team applied the 'Raised Source and Drain (RSD)' structure, a technique conventionally used in silicon processes. The core idea is to deposit additional tellurium to thicken only the areas directly in contact with the electrodes where the current enters and exits (the source and drain). By keeping the current-flowing channel at a thin 4 nm to suppress leakage current while adding extra tellurium to the sections in contact with the metal electrodes, the team allowed the current to flow with significantly improved efficiency. Experimental results demonstrated that devices utilizing this structure experienced a dramatic 50-fold reduction in contact resistance, dropping from 97.5 kΩ·μm to 1.7 kΩ·μm. Furthermore, in an extreme environment of -196°C, the on-state current when the device was fully turned on increased by more than 17 times. The team effectively succeeded in simultaneously achieving both low resistance and high performance within an ultra-thin structure. Notably, this technology can be implemented through a large-area, low-temperature deposition process known as sputtering, ensuring the high scalability required for actual semiconductor mass production. "We have broken through the chronic dilemma of ultra-thin semiconductors—where thinner channels traditionally resulted in higher resistance—with a novel band engineering approach called 'localized thickness control,'" said Professor Byoung Hun Lee of POSTECH. "We expect this to become a core platform technology that can be widely applied not only to tellurium but also to enhancing the performance of various 2D and ultra-thin semiconductor devices, ultimately accelerating the realization of next-generation 3D integrated circuits." This work was supported by the Nanomaterials Development Program and the Core Technology Development Project for National Semiconductor Research Laboratory through the National Research Foundation (NRF) funded by the Ministry of Science and ICT (MSIT), Korea. ▶️ DOI: https://doi.org/10.1021/acsnano.5c18395

"Reading the Invisible": POSTECH-Led Team Develops AI Framework Accounting for Hidden Defects in Metal 3D Printing

Metal additive manufacturing (AM), widely regarded as a revolution in modern manufacturing for its ability to produce lightweight and geometrically complex components, has long faced a critical barrier to widespread adoption: microscopic internal defects that are invisible to the naked eye yet significantly compromise structural integrity. Now, a research team led by Professor Hyoung Seop Kim of POSTECH has harnessed the power of artificial intelligence (AI) to overcome this challenge, marking a major leap forward in the reliability of metal 3D printing technology. Professor Hyoung Seop Kim and integrated M.S.-Ph.D. student Jeong Ah Lee, from the Graduate Institute of Ferrous & Eco Materials Technology and the Department of Materials Science and Engineering at POSTECH, collaborated with Dr. Jeong Min Park's research team at the Korea Institute of Materials Science to develop an AI-based predictive framework capable of accounting for microscopic defects in metal 3D printing processes. The findings were published in Acta Materialia, a leading international journal in materials science. Metal 3D printing works by melting and layering metal powder using a laser, a process known as laser powder bed fusion. During fabrication, small voids called pores can form inside the material, acting like air bubbles that substantially degrade the mechanical strength of finished components. In demanding applications such as aircraft structures and automotive parts, where materials are subjected to extreme conditions, even minor porosity can prove catastrophic. Until now, assessing the effect of such defects required extensive experimentation and considerable time, posing a significant bottleneck in materials development and qualification for safety-critical industries. Rather than attempting to eliminate defects entirely, the research team reframed the problem by focusing on understanding and predicting defects scientifically. The team integrated porosity data alongside process parameters, microstructural features, and mechanical property data to train an AI model. They applied a technique called Data Selection Machine Learning (DSML), which identifies only the most influential variables from the dataset, effectively filtering out noise and focusing the model on the factors that matter most. The approach is analogous to a physician interpreting a CT scan to diagnose disease: the AI analyzes the internal microstructure and defect characteristics of metal components to anticipate their mechanical behavior before any physical testing is performed. A key distinguishing feature of this work is its commitment to interpretability. Rather than delivering a "black box" AI that produces results without explanation, the team employed symbolic regression, an interpretable AI approach, to derive human-readable mathematical equations that describe the predictive model. These equations reflect the underlying physical reality: as porosity increases, the effective load-bearing cross-sectional area decreases, thereby reducing strength. In this way, the AI does not merely predict outcomes; it explains why those outcomes occur, thereby enhancing scientific transparency and trust. To validate the framework, the team fabricated AlSi10Mg alloy, one of the most widely used aluminum alloys in 3D-printed aerospace and automotive components, under a variety of process conditions. The AI-based model successfully predicted the yield strength of components with a Mean Absolute Error (MAE) of just 9.51 MPa within seconds, eliminating the need for complex experimental procedures. This represents more than a 4-fold improvement in prediction accuracy compared to conventional approaches, demonstrating the framework's robustness and practical utility. The research team envisions that this framework can serve as the basis for a "defect-aware design map," enabling the prediction and design of material performance ibased on process conditions in advance, thereby significantly reducing the trial-and-error typically associated with materials development. By making it possible to predict and account for invisible defects at the design stage, this technology has the potential to dramatically accelerate the qualification and commercialization of metal 3D-printed components in industries where safety and reliability are paramount. "We have demonstrated that AI can be used to scientifically understand and control defects," said Jeong Ah Lee, first author of the study. Professor Hyoung Seop Kim added, "This technology will enhance the reliability of metal 3D-printed components and significantly accelerate their commercialization in sectors such as aerospace and automotive industries." This research was supported by the Leading Research Center Program of the National Research Foundation of Korea (NRF), the KIMS Institutional Research Program, and Hyundai Motor Group. Jeong Ah Lee received support from the Next Generation of Researchers Fellowship Program of the National Research Foundation of Korea. ▶️ DOI: https://doi.org/10.1016/j.actamat.2026.122101

Could Sea Squirts' Nano-Packaging Delivery System Help Restore Sea Forests?

[Professor Dong Soo Hwang’s team at POSTECH identifies the marine biological mechanism for packaging and delivering adhesive materials as nanocondensates.] How do sea squirts stay attached to rocks amid crashing waves and strong currents? Recent research has revealed that sea squirts do not simply secrete adhesive substances. Instead, they possess a unique system where they package these materials into nano-sized (nm) condensates, deliver them to the destination, and then unpack them for use on-site. Professor Dong Soo Hwang of the Division of Environmental Science and Engineering, the Division of interdisciplinary Bioscience & Bioengineering, and the Graduate School of convergence Science and Technology at POSTECH has elucidated a previously unknown internal delivery mechanism for underwater adhesive materials in sea squirts by studying their rhizoids1). This study was published in the online edition of the Proceedings of the National Academy of Sciences (PNAS). Around the world, "ocean desertification" — the rapid disappearance of seaweed due to rising water temperatures and pollution—is accelerating. As the seafloor becomes barren, efforts are being made to artificially cultivate seaweed and transplant it back into the ocean. However, a recurring problem has been the seaweed's inability to properly attach to rocks or the seabed during its early growth stages. Although researchers investigated how marine organisms use root-like rhizoids to anchor themselves stably, the complex mechanism remained a mystery. The research team found a crucial clue while analyzing the underwater adhesive proteins secreted from sea squirt rhizoids. They discovered that sea squirts do not secrete adhesive proteins in a simple liquid state. Instead, they combine the proteins with metal ions to create solid nanocondensates, which are tightly packaged within cells for transport. These nanocondensates, coordinated with ions such as iron (Fe), chromium (Cr), and vanadium (V), were found to act as a "protective case," shielding the proteins from the external environment as they move through the body. Once the nanocondensates are secreted outside the cell and reach the cuticle layer of the rhizoid, the particle structure rearranges, activating the adhesive proteins within. Notably, the researchers observed a transition in the role of the metal ions: while they contribute to structural stabilization during transport, they detach and are released during the actual adhesion phase. This mechanism is distinct from the adhesion strategy of mussels, another marine organism. In mussels, the amino acid "DOPA2)" within adhesive proteins binds directly with metal ions to create strong adhesion. In other words, while the binding with metal ions is the core principle of adhesion in mussels, for sea squirts, metal ions play a key role in safely "delivering" the adhesive materials. Sea squirts have uniquely solved the problem of how to deliver the adhesive rather than just the composition of the adhesive itself. This study provides important clues for understanding why seaweed often fails to attach stably to rocks in its early stages. Based on these findings, the research is expected to contribute to the development of bio-adhesives that can assist in the early attachment of seaweed or function reliably in underwater environments. Professor Dong Soo Hwang stated, "The biggest challenge in creating sea forests and cultivating seaweed has been the issue of early attachment, but through this research, we have come to understand the principles of the rhizoid adhesion system. This could become a significant turning point that contributes to addressing climate change, marine ecosystem restoration, and even solving food security issues." This research was supported by Korea Institute of Marine Science & Technology Promotion(KIMST) funded by the Ministry of Oceans and Fisheries. ▶️ DOI: https://doi.org/10.1073/pnas.2526665123 1. Rhizoid: Root like anchoring structures found in seaweeds, tunicates, and hydroids 2. DOPA: 3,4-dihydroxyphenylalanine, Amino acid derivatives contained in mussel adhesive proteins, which play a key role in forming strong adhesion by binding to metal ions.

Thermal ‘tug-of-war’ enables memory with 66× lower energy consumption

[POSTECH and CNU demonstrate spintronic non-volatile switching with up to 66× lower energy consumption] Researchers have developed a memory technology that can store and retain data using almost no electricity by controlling spin states through temperature changes. The work, led by researchers from POSTECH and Chungnam National University, demonstrates non-volatile switching driven by temperature changes rather than electric currents. The approach could reduce energy consumption by up to 66 times compared with existing methods, and by as much as 452 times under ideal conditions. The study was published as an Inside Front Cover paper in Advanced Functional Materials. As artificial intelligence (AI) drives demand for faster and more efficient data processing, energy consumption has become a major constraint. Large data centres already consume electricity on the scale of small cities, increasing the need for low-power memory technologies. One promising candidate is spintronics, which encodes information using the spin of electrons rather than their charge. In such systems, the direction of electron spin represents binary states (0 and 1). Devices based on magnetic insulators are especially attractive because they avoid energy loss casued by current-induced heating. Most existing approaches rely on strong electric currents to switch spin directions, resulting in high energy consumption. Temperature-based methods have been proposed as a lower-power alternative, but the spin orientation typically returns to its original state when the temperature returns to its original value, making non-volatile operation difficult. The researchers overcame this limitation using thermal hysteresis—a phenomenon in which a system does not immediately return to its original state after being heated and cooled, but instead remains stable over a certain temperature range. They built a bilayer structure by stacking two rare-earth iron garnets—gadolinium iron garnet (GdIG) and holmium iron garnet (HoIG). Both materials respond magnetically, but their spin directions change differently with temperature, so that over a specific temperature range they favour different orientations. Strong coupling between the layers, together with the intrinsic magnetic anisotropy of each material, gives rise to bistability—two distinct magnetic orientation states that remain stable within a certain temperature window. The effect can be likened to a tug-of-war game. The two materials act as opposing teams, while temperature strengthens or weakens each side. When one side gains the upper hand, the system shifts in that direction. Like a rope held in place by friction, it does not easily flip back even if the support fades. This persistence is key to non-volatile behaviour, allowing the memory state to remain stable even as external conditions change. The team successfully switched spin directions using only a small temperature change of about ±25 K and a modest magnetic field. Compared with conventional spin–orbit torque (SOT) methods, this approach reduces energy consumption by up to 66 times, and by as much as 452 times under ideal conditions. Professor Hyungyu Jin said, “This study demonstrated that spin states can be controlled and maintained using only temperature changes. It could be an important step toward ultra-low-power memory devices for the AI era.” This work was supported by the Samsung Research Funding & Incubation Center of Samsung Electronics and by grants from the National Research Foundation of Korea (NRF) funded by the Korea government (MSIT). ▶️ DOI: https://doi.org/10.1002/adfm.202527195

"Breaking the Limits of OLED: POSTECH Achieves Low-Votage Freely Color Tunable Ultra-Pure Laser Emission"

[Hyper performing Laser emission technology based on OLED –liquid crystal platforms achieving tens-fold enhanced color purity over OLEDs and continuous wavelength tuning over 135 nm at 1.5 V operation] A new class of laser emission technology enabling ultra-high color purity and continuous spectral tunability at low voltage has been developed, marking a significant advance beyond conventional display light sources. A research team led by Prof. Su Seok Choi of the Department of Electrical Engineering at POSTECH —including Hyerin Kim (M.S.), Jeongwoo Park (integrated M.S.-Ph.D. program), and Wontae Jung (Ph.D. candidate) among others—has demonstrated a next-generation laser emission platform capable of precise color control under battery-level low voltage. The study was selected as an Inside Front Cover article in the international optics journal Laser & Photonics Reviews, underscoring its scientific significance. The clarity and purity of color are fundamentally determined by how narrowly light is confined within a specific wavelength range, typically quantified by the full width at half maximum (FWHM) of the emission spectrum. Conventional OLED-based displays exhibit relatively broad emission spectra (FWHM ~40 nm), while even advanced quantum dot (QD) emitters remain around ~30 nm. These intrinsic spectral limitations restrict color purity and pose critical challenges for emerging applications such as holographic and advanced AR/VR displays, which require laser-like ultra-narrowband (~1 nm) emission for precise optical wavefront and phase control. In addition, existing display technologies rely on the color mixing of discrete red–green–blue (RGB) emitters, leading to structural complexity and limited capability for continuous spectral tuning. Achieving both ultra-high color purity and continuous wavelength tunability within a single device has remained a long-standing challenge. To address these limitations, the research team introduced a novel photonic architecture that integrates OLED emissive materials with chiral liquid crystals (CLCs). The helically ordered structure of CLCs forms a periodic resonant cavity capable of selectively amplifying specific wavelengths. By coupling broadband OLED emission into this chiral resonant structure, the team successfully transformed it into laser-like emission with an ultra-narrow linewidth of approximately 1 nm (FWHM), achieving color purity tens of times higher than that of conventional OLEDs. Beyond spectral narrowing, the team also achieved continuous wavelength tunability within a single device. By employing an electrothermal actuation mechanism, small electrical inputs induce controlled thermal modulation of the CLC helical pitch, thereby shifting the resonance wavelength. Notably, this enables continuous color tuning over a wide visible spectral range of approximately 135 nm under a low driving voltage below 1.5 V, overcoming the high-voltage limitations of conventional tunable laser systems. Importantly, the proposed platform achieves this functionality within a single-pixel architecture. Unlike conventional displays that require multiple RGB subpixels, the device can generate a continuous spectrum of colors from a single emissive unit, significantly simplifying the device structure and enabling high integration density for future display and photonic systems. This work is particularly notable in that it realizes ultra-high-brightness emission together with low-voltage, color-tunable vertical-cavity lasing—key attributes for next-generation display applications. This work represents a comprehensive breakthrough that simultaneously overcomes three key limitations of conventional light sources: high driving voltage, broad emission spectra, and complex multi-emitter architectures. By integrating low-voltage operation, ultra-high color purity, and continuous spectral tunability into a unified platform, the technology opens new possibilities for next-generation photonic applications. Potential applications include holographic displays, AR/VR and micro-displays, ultra-high color gamut imaging systems, wavelength-tunable optical communications, biosensing, optical encryption, and next-generation photonic semiconductor devices for AI. Professor Choi commented, “By combining OLED materials with chiral liquid crystals, we have demonstrated laser-grade ultra-high color purity emission and precise wavelength control at practical low voltages. This work establishes a new platform that could fundamentally transform the architecture of displays and optoelectronic devices.” This research was supported by the Samsung Future Technology Foundation under its designated display research program. ▶️ DOI: https://doi.org/10.1002/lpor.202502740

Body-Compatible Electrode Developed: Rigid on Insertion, Soft Once Inside

[POSTECH researchers develop a bio-implant with virtually no immune response at the cellular and tissue level] Pohang, South Korea — A research team at POSTECH has developed a novel electrode that the human body does not reject. This breakthrough addresses a fundamental limitation of current wearable technology and is attracting significant attention from the academic community. A team led by Professor Geunbae Lim of the Department of Mechanical Engineering, together with Dr. Jungho Lee and Dr. Gaeun Yun, in collaboration with Professor Sung-Min Park and Professor Chulhong Kim, has developed a ‘Dermal Bioelectrode (Dermal Electronics)’ that minimizes pain and inflammation while enabling stably biosignal measurement unaffected by external environmental factors. The study has been published as a Front Cover article in Advanced Materials, a leading international journal in the field of biomaterials. As smartwatches measure heart rates and adhesive patches monitor blood glucose levels, wearable devices have become integral tools for everyday health management. However, the electrode technology that enables these devices still faces structural limitations. Epidermal electrodes attached to the skin surface are convenient to use but produce unstable signals due to sweat, dryness, and body movement. In contrast, microneedle electrodes inserted into the skin offer greater signal accuracy but can cause tissue irritation and inflammatory responses because of their rigid structure. As a result, users have long been forced to choose between convenience and reliability. The team’s electrode is rigid like a needle at the moment of insertion—stiff enough to penetrate the stratum corneum—but transforms into a soft, compliant structure once it reaches the dermal layer. The concept draws on the same principle by which aluminum serves as a strong alloy in aircraft yet becomes a thin, pliable foil in the kitchen: identical materials can exhibit entirely different mechanical properties depending on their structural design. The key enabling technologies are ultra-precision micro-fabrication of highly flexible biomaterials and an effervescent structural transformation mechanism. An effervescent sacrificial layer allows the electrode to pass through the stratum corneum within seconds, after which it settles stably into the dermis. Once in the dermal layer, the electrode becomes inherently flexible, minimizing the mechanical stress imposed on surrounding cells and tissues. In effect, the body recognizes the electrode not as a foreign object but as a structure capable of coexistent. Through experiments on both animal models and human subjects, the team confirmed that virtually no tissue damage or immune response occurs even during prolonged implantation. Moreover, the electrode’s stable positioning within the dermal layer renders it immune to changes in the external environment: signal accuracy remained consistent under conditions of perspiration, dehydration, and extended wear. This research goes beyond incremental improvements in wearable electrodes; it expands the signal acquisition zone from the skin surface to the dermal layer—a significant shift in biosignal measurement. “This technology can extend beyond medical diagnostic devices to next-generation ‘Physical AI’ systems that precisely collect biometric data and integrate it with artificial intelligence,” said Professor Lim. “It marks the starting point for a new class of data-driven technologies that continuously understand and leverage human biometric information.” The rapid advancement of artificial intelligence is bringing humanoid robots and virtual reality closer to everyday life. Controlling a robot’s precise movements and driving virtual avatars require high-dimensional, accurate interpretation of biosignals. In medical and industrial settings, acquiring reliable biometric data is considered a core requirement for robot actuation. This study elevates the depth and reproducibility of biosignal collection and interpretation, strengthening the connection between software and hardware—an advancement expected to play a pivotal role in the development of next-generation interface technologies. ▶️ DOI: https://doi.org/10.1002/adma.202509719

Climate-Driven Extreme Fire Danger Cannot Be Prevented by Carbon Neutrality Alone

[POSTECH Professor Seung-Ki Min’s Research Team Compares Future Extreme Fire Weather Under ‘Net-Zero’ vs. ‘Net-Negative’ Emission Scenarios] A new study warns that unless atmospheric carbon is reduced immediately, future summers will become even hotter and future wildfires even more destructive. A research team led by Professor Seung-Ki Min of the Department of Environmental Engineering at POSTECH has found that merely achieving “carbon neutrality” by reducing emissions is not sufficient to significantly reduce extreme wildfire risk. The team argues that active “carbon reduction” - removing carbon dioxide already accumulated in the atmosphere - must be pursued in parallel. The study was recently published in Science Advances. Large-scale wildfires are becoming more frequent and more intense worldwide. Each year, thousands of people lose their lives, ecosystems are devastated, and enormous economic losses are incurred. Wildfires are often viewed as disasters triggered by ignition sources such as lightning strikes, discarded cigarettes, or human negligence. However, the real driver lies elsewhere. Large wildfires are fundamentally driven by climate conditions shaped by temperature, humidity, and wind. As temperatures rise and the air becomes drier, forests become tinderboxes, allowing fires to burn longer and spread farther. Using climate simulations, the POSTECH research team compared two possible futures. One scenario achieves carbon neutrality by reducing carbon dioxide emissions to “net-zero” levels. The other goes further by implementing carbon reduction measures aimed at achieving “net-negative” emissions, thereby lowering the concentration of carbon dioxide already present in the atmosphere. The results were clear. Under the net-zero scenario, extreme fire danger remained high across many parts of the world. In some low-latitude regions of the Northern Hemisphere, the danger even increased. In contrast, under the net-negative scenario, declining atmospheric CO₂ concentrations led to lower temperatures and higher humidity, substantially reducing the conditions conductive to wildfires. These mitigating effects were particularly pronounced in regions already highly vulnerable to wildfires. These findings cannot be explained by temperature changes alone. Atmospheric carbon dioxide concentrations influence large-scale oceanic and atmospheric circulation systems, reshaping precipitation patterns and temperature distributions worldwide. Changes in major climate systems, such as the Atlantic Meridional Overturning Circulation and shifts in the Intertropical Convergence Zone, play a critical role in determining regional fire weather danger. The study delivers a clear message: carbon neutrality is not the endpoint of climate action, but its starting point. Just as turning off a faucet does not remove water that has already overflowed, halting emissions alone cannot reverse climate change that is already underway. Carbon reduction - including carbon capture and storage technologies, carbon removal technologies, and nature-based solutions such as forest restoration - is therefore essential. This implies that policy and technological development across energy, environmental management, urban planning, and disaster response must be fundamentally reoriented. The research demonstrates that a carbon-neutral world is not necessarily a safe one. Professor Min stated, “Carbon neutrality only stops further increases in extreme fire risk; it is not a solution for reversing the danger that has already intensified. To protect societies and ecosystems from extreme wildfires, we need net-negative emission strategies that go beyond carbon neutrality.” This study, conducted by Professor Seung-Ki Min and Dr. Yujin Kim of POSTECH’s Department of Environmental Engineering, was supported by the Mid-Career Researcher Program of the National Research Foundation of Korea. ▶️ DOI: https://doi.org/10.1126/sciadv.adw4705