Search

Barcodes are utilized for product information management in shops, offices, hospitals, passenger facilities, and factories because they enable substantial amounts of data to be processed quickly and accurately. However, a limited amount of information can be loaded on the currently used monochrome barcodes that are based on thin-film coatings. Therefore, these barcodes require constant replacement with new barcodes to update the information; furthermore, they cannot be applied to textile products. This study demonstrated the performance of wearable invisible infrared (IR)-emitting barcodes by using twisted yarns that comprised five highly elastic/conductive spandex fibers. The barcode information can be actively updated via the selective IR emission from specific yarns of the barcode by controlling the applied voltage to the IR-emitting yarns. Therefore, the IR barcode required a relatively small number of bars to express a higher volume of information compared to the existing monochrome barcodes. Because the emitted IR light from the yarns was invisible to the human eye and was only recognized by an IR camera, the information-variable IR-emitting yarn-based barcode exhibited an aesthetic design and was composed of a sustainable fabric-type material that could be easily applied to clothes, bags, and shoes. It is expected that the fabricated barcode will be widely utilized as wearable invisible barcodes, whose information will remain invisible to humans and can be updated in real time to ensure information fluidity.

The structural, magnetic and ferroelectric properties of polycrystalline A-site (A = Ho, Pr and Ce of 10%) doped BiFeO3, which were prepared by the solid-state and rapid sintering methods, have been investigated. The powder X-ray diffraction pattern reveals that all the samples show rhombohedral perovskite structure R3c. The Ho-doped BiFeO3 shows that the magnetic property is slightly increased due to compressive lattice distortion and Ho3+ ion doping effect. For the Pr and Ce doped BiFeO3, the remnant polarization and coercive field increased because Pr3+ and Ce3+ ions substitution suppressed oxygen vacancies.

The periodic arrangement in metamaterial (MM) should be maintained to ensure the extraordinary properties, but how much periodic irregularity is allowed generally without degrading the properties is not only important for the tolerance in fabrication but interesting scientifically. We introduce the wrecked effect in MM utilizing perfect MM absorber in visible and GHz ranges. The original perfect MM properties turn out to be maintained until MM is destroyed to 10%. In the view of MM absorber, even 40% broken meta-pattern are still good for absorption higher than 93%, the criterion for perfect absorption. The wrecked pattern over 80% result in absorption of nearly 50% in both simulation and experiment, which is even higher than expected. These results can lead to broad applications at the present and in near future through more convenient and cost-effective research and development on MMs.

We simulated a study on a tunable metamaterial absorber using ferrite rubber as a dielectric substrate with ferromagnetic properties. The proposed structure employs ferromagnetic resonance, which utilizes the coupling of an applied magnetic field and an incident electromagnetic wave. As the magnitude of the applied magnetic field increases, it can be seen that the absorption peak moves to a higher frequency. The adjustment of the absorption frequency using the proposed method is expected to be applied to various fields such as sensors, electronic devices and 5G communication antennas.

We studied the adsorption of nitrogen oxides according to various porous materials room temperature, which can effectively to adsorb the nitrogen oxides. Based on results of measuring NOx concentration, the activated carbon materials have been shown to adsorb NOx well, and they have been shown to more efficiently removing NO2, which is very harmful to the environment. In particular, in the case of the coconut activated carbon, the removal efficiency of NO and NO2 was very excellent, and the removal rate of was 30% for 100 minutes and 19.5% for 840 minutes. Our measurement results confirmed that the activated carbon materials have a very large specific surface area and pore volume. In addition, the coconut activated carbon appears to have a large specific surface area and pore volume to remove NOx over a long period of time. Based on the experimental results, it is expected to be used as a material that efficiently removes nitrogen oxides at room temperature.

Polydimethylsiloxane (PDMS), an optically transparent and inert material, is widely used in biological and semiconductor applications owing to its excellent chemical stability and moldability. This study proposes a thermally induced wet spinning method for the fabrication of long PDMS fibers with a constant width. PDMS is a thermoset polymer that undergoes chemical crosslinking when heated, and the thermally induced wet spinning process allows for the formation of fibers without a mold. A rapid thermal curing step was used to instantly solidify the thermoset polymer, where immediate chemical crosslinking of fluid PDMS solution was achieved upon contact with an oil coagulation bath at 180–230 °C. A rapid stretching process was applied to pull out and control the width of the fiber, and the PDMS was stretched at a rate of 1.2–12.5 m/min during the crosslinking process. The fabricated pristine PDMS fibers were transparent and maintained a crosslinked network with excellent mechanical strength. In addition, the PDMS fibers were functionalized with silica nanoparticles, carbon nanotubes, and pores to adjust their transparency/opacity, conductivity, and heat insulation properties, respectively, for various applications. The proposed thermally induced wet spinning method shows promise for overcoming the limitations of existing molding methods, in which the PDMS fibers cannot be lengthened. Furthermore, the process is environmentally friendly and economical owing to the use of edible canola oil, which reduces the volume of harmful solvents and additives during fiber production.

In this paper, we studied the heat flux effect of thermal metamaterials according to the distance of each layer, which can effectively suppress heat propagation and improve an adiabatic property, through the three-dimensional finite-difference time-domain simulation. Based on multiple layers of thermal meta-materials, the heat flux in the propagation direction could be suppressed by thermal meta-layers. The heat flux transferred through the gap between thermal meta-layers could also be efficiently suppressed by controlling the gap of each meta-layer in a concrete block. It was found that the heat transfer characteristics and the thermal insulation efficiency can be adjusted according to the change of the distance in the 5-layers meta-structure. Furthermore, the adiabatic property greatly changed depending on the location of the heat source and the thermal meta-structure transferred into the concrete. The appropriate thickness of each meta-layer should be used to suppress heat transfer and improve adiabatic properties in the concrete structure from the results of the 10-layer meta-structure.

Owing to the increasing interest in personal health, the real-time measurement of the exposure to ultraviolet (UV) rays during outdoor activities is a key technology that could be widely applied in the field of smart healthcare. Although wearable sensors that respond to UV intensity are being investigated, the development of sensors with stable durability and excellent sensing characteristics, despite movements, such as bending and exposure to external factors, including sweat and rain, is insufficient. In this study, we fabricated a wearable UV fiber sensor by embedding conductive carbon nanotubes (CNTs) and UV-sensitive zinc oxide nanowires (ZnO NWs) into highly elastic spandex fiber via a simple dipping-drying procedure. The ZnO NWs and CNTs coated in the form of a network inside the strands that constitute the spandex fiber enhanced the stability of the UV sensing measurements despite external changes, such as bending. In addition, by coating hydrophobic (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)phosphonic acid onto the ZnO NWs, the current distortion of the UV sensing channel due to contact with liquid could be prevented. It was confirmed that the fiber-based UV sensor, in which ZnO NWs and CNTs are networked, responds sensitively to UV in an environment with exposure to water or sweat.

A smart window, which can easily adjust light transmittance, can provide barrier functions, such as improvement in energy efficiency, glare prevention, and privacy protection. However, a smart window that can selectively provide real-time information and display various colorful characters and images at a desired location has not been developed. In this study, a novel smart window capable of real-time information conversion is developed by advancing the light transmittance control of the existing smart windows. A transparent and flexible window display is fabricated by synthesizing poly(N-isopropylacrylamide) (pNIPAM)-N,N-methylenebisacrylamide-crosslinked hydrogels (NBcH) and near-infrared (NIR) absorption-heating films sandwiched between two plastic substrates. When the NIR laser irradiates the window display panel surface, the temperature rises rapidly, as the NIR absorption-heating film absorbs the NIR wavelength. The generated heat is transferred to pNIPAM in contact with the NIR absorption-heating film, and an image forms in real time. In addition, if the NIR laser and projector simultaneously irradiate the window display panel surface, various colorful images can be displayed. The smart window for real-time information provision proposed in this study acts like a glass curtain that can selectively make a desired location transparent or opaque by controlling the transmittance of light and acts as a display that can present various colorful characters and images in real time. Therefore, it is expected to be highly convenient for users.

Plastics are used in cover substrates for billboards, windows, large LED signboards, lighting devices, and solar panels because they are transparent and can be colored and shaped as desired. However, when plastic cover substrates installed in outdoor environments are constantly exposed to harsh conditions such as snow, rain, dust, and wind, their transparency deteriorates owing to watermarks and dust contamination. Herein, we investigated a simple dipping-press coating method that can impart hydrophobicity while maintaining the transparency, regardless of the plastic substrate type. A highly transparent and hydrophobic coating film was formed on a plastic substrate by a two-step process, as follows: (1) application of a polydimethylsiloxane&ndash, octadecylamine coating by a dipping process, and (2) embedding (1H,1H,2H,2H-heptadecafluorodec-1-yl) phosphonic acid&ndash, aluminum oxide nanoparticles by a thermal press process. The plastic substrates on which the highly transparent and hydrophobic coating film was formed showed 150&deg, or higher hydrophobicity and 80% or higher visible light transparency. The coating method proposed herein can easily impart hydrophobicity and is compatible with any plastic substrate that must maintain prolonged transparency without contamination when exposed to adverse conditions.

With the increasing trend of high-rise, large-scale, and functional modern architectural structures, lightweight aggregate (LWA) concrete that exhibits excellent strength and high functionality has garnered active research attention. In particular, as the properties of concrete vary considerably with the raw materials and the proportions of aggregates in the mix, in-depth research on weight reduction, strength improvement, and functional enhancements of aggregates is crucial. This study used the negative pressure coating of a mixed solution comprising epoxy (mixture of epoxy resin and crosslinker), hyper-crosslinked polymer, and titanium oxide (TiO2) nanoparticles on the LWA, and achieved an improvement in the strength of the LWA as well as a reduction in air pollutants such as NOx and SOx. Compared to a normal LWA with an aggregate impact value (AIV) of 38.7%, the AIV of the proposed epoxy–TiO2-embedded high-strength functional LWA was reduced by approximately half to 21.1%. In addition, the reduction rates of NOx and SOx gases resulting from the photocatalytic properties of TiO2 nanoparticles coated with epoxy were approximately 90.9% and 92.8%, respectively. Epoxy–TiO2, embedded in LWAs through a mixture, exhibited stability, high strength, and a reduction in air pollutant characteristics, despite repeated water washing. The LWA proposed herein offers excellent structural and functional properties and is expected to be used in functional lightweight concrete that can be practically applied in high-rise and large-scale architectural structures.

Here, we investigate a wearable-based IR and thermal stealth structure that effectively blocks IR and thermal radiation from a human body or device using a polyurethane–antimony tin oxide (PU–ATO) composite fiber. The aging time of the ATO sol prepared by a sol–gel method, and the concentration of ATO with respect to that of the PU matrix were optimized to prepare PU–ATO composite fibers that simultaneously have an appropriate mechanical strength (strength of ~4 MPa and strain of ~340%) and IR- and thermal radiation-shielding properties with ~98% IR light, as determined by Fourier transform IR spectroscopic studies. The fabricated PU–ATO composite fiber showed stable IR- and thermal radiation-shielding properties even when exposed to ten cycles of repeated temperature changes of −20 and +80 °C and long-term temperature changes for 30 days. In addition, the surface of the PU–ATO composite fiber was rendered hydrophobic to prevent the distortion of the IR and thermal radiation due to the wetting of the PU–ATO composite fiber with absorbed water. The PU–ATO composite fiber-based textile proposed herein can be applied in wearable IR- and thermal radiation-shielding technologies to shield IR signals generated by objects of diverse and complex shapes. A material that makes us invisible to infrared cameras has been developed by researchers in South Korea. Even in total darkness, the heat that our body produces can give away our position. Clothing that masks this infrared radiation to make the wearer indistinguishable from the background is therefore useful in stealth applications. Sang Yoon Park from Seoul National University, Sanghyun Ju from Kyonggi University, Suwon, and their colleagues have developed a fiber made from a combination of a polymer known as polyurethane and a metal oxide, antimony tin oxide (ATO). The fibers block thermal radiation because the ATO scatters infrared light. The team used a wet-spinning technique to create a number of different composite fiber with varying ATO concentrations so that they could optimize their useful lifetime. The polyurethane–antimony tin oxide (PU–ATO) composite fibers makes infrared (IR) radiations emitted by an object to be as similar as possible to ambient background radiation such that an IR detection sensor fails to distinguish the target object. Hydrophobic surface of the PU–ATO composite fiber prevent the distortion of the IR and thermal radiation caused by the wetting of the PU–ATO composite fiber with water. The PU–ATO composite fiber-based textile can be applied in wearable IR- and thermal radiation-shielding technologies to shield IR signals generated by objects of diverse and complex shapes.

Despite the great potential of polymer microfibers in human-friendly wearable electronics, most previous polymeric electronics have been limited to thin-film-based devices due to practical difficulties in fabricating microfibrillar devices, as well as defining the active channel dimensions in a reproducible manner. Herein, we report on conducting polymer microfiber-based organic electrochemical transistors (OECTs) and their application in single-strand fiber-type wearable ion concentration sensors. We developed a simple wet-spinning process to form very conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) microfibers using aqueous sulfuric acid solutions and carefully examined their electrical/electrochemical properties. In conjunction with fabricating substrate-free PEDOT:PSS microfiber-based OECT devices, the proposed novel characterization method demonstrated that the current variation ratio can be a reliable method for evaluating the device performance for sensing ion concentrations, regardless of the actual channel dimensions. Finally, we developed single-strand fiber-type skin-mountable OECTs by introducing a source-gate hybrid electrode and demonstrated that the resultant microfiber sensors can perform real-time repetitive measurements of the ion concentration in human sweat. A wearable device that analyses sweat and could help athletes optimize their intake of fluids and electrolytes has been developed by researchers in South Korea. Wearable electronics provide a way to monitor the body around the clock, and even deliver simple healthcare solutions. Such devices need to be light, robust, and flexible enough to adapt to the wearer’s movement. Sanghyun Ju from Kyonggi University in Suwon, Myung-Han Yoon from Gwangju Institute of Science and Technology and their colleagues have made a wearable device that can measure the ion concentration in human sweat. Previous materials used in such devices required a substrate, which limited their mechanical flexibility. Instead, Ju, Yoon and the team created highly conductive microfibers, which they used to fabricate electrochemical transistors. The current through the transistor varied with ion concentration, enabling real-time measurements. In textile electronics, micro to millimeter-scaled misalignment is commonly occurred during the high-throughput and bulk-scaled textile manufacturing process, thus the exact performance control of the fiber-based active devices is very difficult in low-cost wearable electronics. In this research, we developed novel single-strand organic electrochemical transistors and proposed dimension-independent characterization method (i.e., the current variation ratio in variation of logarithmic concentration of electrolyte) for ion concentration sensing. Furthermore, we demonstrated the pseudo two-terminal transistor operation by incorporating electrochemical gate electrode onto the surface of the source electrode, leading to single-strand fiber device platform.

In this study, we investigated the reduction of a 3D microporous NiOx structure, used as a metal oxide catalyst, by proton irradiation with polyvinylpyrrolidone (PVP) for hydrogen regeneration. In general, the reduction process for hydrogen regeneration requires high temperatures (1000–4000 °C) to release saturated oxygen from the metal oxide catalyst. Proton irradiation with PVP could regenerate abundant oxygen vacancies by releasing the oxygen attached to NiOx at room temperature. The 3D microporous NiOx structure provided the maximum hydrogen generation rate of ∼4.2 μmol min−1 g−1 with the total amount of generated hydrogen being ∼460 μmol g−1 even in the repetitive thermochemical cycle; these results are similar to the initial hydrogen generation data. Therefore, continuous regeneration of hydrogen from the oxygen-reduced 3D microporous NiOx structure was possible. It is expected that the high thermal energy, which is the major problem associated with hydrogen regeneration through the conventional heat treatment method, would be resolved in future using such a method.

In this study, we developed a method to detect small amounts of chemical substances contained in water by using a SnO2 nanowire transistor covered with an aerogel microsphere thin film. The aerogel microsphere thin film acts as a liquid-vapor separation filter, allowing the passage of chemical vapor while blocking liquid chemicals and water. The concentration of chemical substances, such as toluene, nitric acid, benzene, and chloroform, in water could be estimated by evaluating the current changes in the SnO2 nanowire transistor covered with the aerogel microsphere thin film. The time-dependent response of the device depending on the chemicals in water was repeatedly observed for multiple cycles, which demonstrated that the response and recovery properties were reproducible.

The amount of hydrogen gas generated from metal oxide materials, based on a thermochemical water-splitting method, gradually reduces as the surface of the metal oxide oxidizes during the hydrogen generation process. To regenerate hydrogen, the oxygen reduction process of a metal oxide at high temperatures (1000–2500 °C) is generally required. In this study, to overcome the problem of an energy efficiency imbalance, in which the required energy of the oxygen reduction process for hydrogen regeneration is higher than the generated hydrogen energy, we investigated the possibility of the oxygen reduction of a metal oxide with a low energy using microwave irradiation. For this purpose, a macroporous nickel-oxide structure was used as a metal oxide catalyst to generate hydrogen gas, and the oxidized surface of the macroporous nickel-oxide structure could be reduced by microwave irradiation. Through this oxidation reduction process, ∼750 μmol g−1 of hydrogen gas could be continuously regenerated. In this way, it is expected that oxygen-enriched metal oxide materials can be efficiently reduced by microwave irradiation, with a low power consumption of

In general, infrared (IR) images are generated based on the temperature distribution of the objects of interest by detecting the thermal IR radiation emitted from these objects with the help of sensors. However, the generation of information-specific IR images can enable “intelligent” entities such as autonomous vehicles and artificial intelligence robots with IR detection features to use IR images for exchanging information. In this context, here, we examine a method of realizing IR-image-based information using IR laser projection. With our approach, two- and three-dimensional IR images could be generated by converting near-IR rays to far-IR rays based on the heat generated by a laser. Importantly, the IR signals do not adversely affect humans or interfere with electronic devices. The proposed IR display can be used to exchange specific information among IR-detection-enabled entities without being detected by the human eye. Therefore, it is expected to overcome the problem of light pollution due to the indiscriminate use of displays and human-health-related problems arising from the exposure to electromagnetic wave-based information transmission.

Abstra ct In this work, graphene was treated by tetrafluoromethane (CF 4 ) plasma to investigate the effect on its wettability. Fluorine was adsorbed on the graphene surface after the plasma treatment, and the contact angle of the fluorine-functionalized graphene increased to ~ 104.9° from ~ 66.7° for pristine graphene. The durability of the fluorine-functionalized graphene samples was tested as a function of time, and the samples were found to have stable hydrophobic properties, which suggests that a robust chemical bond was formed between fluorine and the graphene surface. Our results demonstrate that the use of plasma techniques to control the wetting characteristics of graphene is a low-cost and highly reliable method that is well suited for the fabrication of low-friction materials for various applications.

Lightweight nano/microscale wearable devices that are directly attached to or worn on the human body require enhanced flexibility so that they can facilitate body movement and overall improved wearability. In the present study, a flexible poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) fiber-based sensor is proposed, which can accurately measure the amount of salt (i.e., sodium chloride) ions in sweat released from the human body or in specific solutions. This can be performed using one single strand of hair-like conducting polymer fiber. The fabrication process involves the introduction of an aqueous PEDOT:PSS solution into a sulfuric acid coagulation bath. This is a repeatable and inexpensive process for producing monolithic fibers, with a simple geometry and tunable electrical characteristics, easily woven into clothing fabrics or wristbands. The conductivity of the PEDOT:PSS fiber increases in pure water, whereas it decreases in sweat. In particular, the conductivity of a PEDOT:PSS fiber changes linearly according to the concentration of sodium chloride in liquid. The results of our study suggest the possibility of PEDOT:PSS fiber-based wearable sensors serving as the foundation of future research and development in skin-attachable next-generation healthcare devices, which can reproducibly determine the physiological condition of a human subject by measuring the sodium chloride concentration in sweat.

In nature, many cells possess cilia that provide them with motor or sensory functions, allowing organisms to adapt to their environment. The development of artificial cilia with identical or similar sensory functions will enable high-performance and flexible sensing. Here, we investigate a method of producing artificial cilia composed of various polymer materials, such as polyethylene terephthalate, polyurethane, poly(methyl methacrylate), polyvinylpyrrolidone, polystyrene, polyvinyl chloride, and poly (allylamine hydrochloride), using a field effect spinning (FES) method. Unlike wet- or electro-spinning, in which single or multiple strands of fibers are pulled without direction, the FES method can grow fiber arrays vertically and uniformly on a substrate in cilia-like patterns. The lengths and diameters of the vertically grown artificial cilia can be controlled by the precursor polymer concentration in the solution, applied electric current and voltage, and shape and size of the needle tip used for FES. The red, green, and blue emission characteristics of the polymer-quantum dot-based self-emitting artificial cilia prepared in polymer-inorganic nanoparticle hybrid form were determined. In addition, an artificial cilia-based humidity sensor made of the polymer-polymer composite was fabricated.

An invisibility cloak based on visible rays with a refractive index similar to that of air can effectively conceal people or objects from human eyes. However, even if an invisibility cloak based on visible rays is used, an infrared (IR) thermography camera can detect the heat (thermal radiation) emitted from different types of objects including living things. Therefore, both visible and IR rays should be shielded using an invisibility cloak produced by an appropriate technology. Herein, we developed a textile cloak that can almost completely conceal people or objects from IR vision. If a person or object is covered with an IR- and thermal-radiation-shielding textile woven with polyurethane (PU)-tin oxide (SnO

The precise control of the threshold voltage ( V th ) required to turn a metal-oxide semiconductor field-effect transistor on/off at the designed voltage was important to ensure that the V th was constant for all the transistors in the circuit. In this study, V th was adjusted in both the negative and positive directions by manipulating the number of O vacancies on the surface of an oxide nanowire channel using ultraviolet (UV) and UV-ozone (UVO) irradiation. UV irradiation shifted the V th in the negative direction by an amount that increased with increasing exposure time (−0.96 V at 1 min, −1.42 V at 2 min, and −1.70 V at 3 min), whereas UVO irradiation shifted the V th in the positive direction by an amount that increased with increasing exposure time (+0.37 V at 3 min, +0.69 V at 5 min, and +1.07 V at 10 min). The shifted values of V th were maintained by passivating the channel region of the oxide nanowire with an octadecylphosphonic acid self-assembled monolayer.

Highly flexible and stretchable graphene-based fibers are one of the most synthetically challenging materials that are suitable for next-generation wearable electronics. Graphene-based fibers used in reliable wearable devices should be multifunctional and stable. Here, we report an easy-handling fabrication method for reduced graphene oxide fibers containing semiconducting CuI and metallic Cu particles (CRGO fiber). The fibers were prepared by wet spinning and hydriodic acid treatment from a CuCl2–ethylene glycol coagulating solution without pre-synthesized CuI and Cu particles. The fabricated CRGO fibers exhibited chemical sensitive/temperature insensitive or chemical insensitive/temperature sensitive characteristics, depending on the Cu concentration in the CRGO. This is the first demonstration of a highly selective chemical and temperature sensor with sensitivity-switching properties fabricated from twisted CRGO fibers comprising two fiber bundles with low and high Cu concentrations.

In this study, we report the utilization of a three-dimensional (3D) porous graphene structure as liquid–vapor separation filter, which allows the passage of chemical vapors while blocking liquid chemicals and water. The blockage of liquid chemicals and water from semiconducting sensing regions is required to avoid abnormal transistor characteristics. In order to impart omniphobic characteristics, a (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trichlorosilane (HDF-S) self-assembled monolayer was coated on the surface of the 3D porous graphene structure. The concentration of chemical agents in water could be consistently detected by observing the shift in the threshold voltage in the oxide nanowire transistor covered by the HDF-S self-assembled 3D graphene structure. The proposed monitoring method is expected to offer means for application in different environments by providing a stable sensing performance.

The human eye cannot recognize the shape of an object behind an opaque substrate; however, by reading and imaging infrared (IR) rays emitted from such an object, its shape behind the opaque substrate can be ascertained. In this study, an infrared double-sided light-emitting display was deposited on an opaque substrate and the transmission characteristics of infrared rays were measured under various conditions, such as changes in the thickness of the opaque substrate, the distance between the opaque substrate and the object, the infrared intensity of the object, and the viewing angle of the object. By selecting an opaque substrate material suitable for an IR display, the IR transmittance and heat diffusivity were improved. Additionally, by controlling the IR intensity of the IR emitter patterned on the opaque substrate, display information of various colors could be expressed from the IR vision, similar to the RGB wavelength separation of visible light. This technology deviates from the stereotype that a double-sided light-emitting display should use a transparent substrate and demonstrates that a double-sided light-emitting display can be made of an opaque substrate material if the light emission characteristics of IR rays are efficiently controlled.

Infrared (IR) display technology implements a display using IR radiation. Whereas ordinary visible displays that output digital data in the visible spectral range are detectable to human eyes, an IR display outputs data outside the visible spectral range. This study looks at the possibility of expanding the color-replication spectrum beyond the visible range by applying IR wavelength separation techniques. We developed a new display technology that uses the same driving method as general display technology but emits IR radiation that cannot be seen by humans. The IR wavelength region was separated into three regions, similar to the RGB regions of visible displays, and an IR display capable of outputting images and movies was produced by combining these IR emissions. The implementation of various characters, figures, and videos was demonstrated. The present method can be applied to the production of single displays based on IR radiation, as well as to the production of multi-displays whereby an IR display is mounted on top of a visible light display on a single device. This technology can be used to provide a smart digital information environment where humans can selectively visualize or conceal information.

The implementation of complete infrared (IR) camouflaging/disguise technology requires three-dimensional (3D) thermal camouflage that can respond rapidly to changes in the ambient temperature and operate uniformly at various angles. In this study, a fiber-based IR conductive material was developed that responds sensitively and rapidly to changes in the ambient temperature. Moreover, the material can be woven into various patterns, enabling the IR camouflage of a 3D wearable garment. A full-color IR radiation image is produced by generating three different IR intensities based on the voltage applied to a far-IR fiber. The use of passive camouflage technology enables objects to be hidden from their backgrounds, while active camouflage technology permits objects to be camouflaged against changing surrounding backgrounds or to be recognized as arbitrary objects (e.g., car, animal, or plant). It is expected that this differentiated camouflaging/disguise technology based on IR imaging can be applied to various industrial, military, and new scientific fields.

Flexible fibers composed of a conductive material mixed with a polymer matrix are useful in wearable electronic devices. However, the presence of the conductive material often reduces the flexibility of the fiber, while the conductivity may be affected by environmental factors such as water and moisture. To address these issues, we developed a new conductive fiber by mixing carbon nanotubes (CNT) with a polyurethane (PU) matrix. A silane ((heptadecafluoro&ndash, 1,1,2,2&ndash, tetra&ndash, hydrodecyl)trichlorosilane) was added to improve the strain value of the fiber from 155% to 228%. Moreover, silica aerogel particles were embedded on the fiber surface to increase the water contact angle (WCA) and minimize the effect of water on the conductivity of the fiber. As a result, the fabricated PU-CNT-silane-aerogel composite microfiber maintained a WCA of ~140&deg, even after heating at 250 &deg, C for 30 min. We expect this method of incorporating silane and aerogel to help the development of conductive fibers with high flexibility that are capable of stable operation in wet or humid environments.