Abstract Optical see-through augmented reality (AR) displays must render vivid virtual imagery overlaid on a faithful view of the background real-world under ambient illumination. In this scenario, the virtual channel (VC) and real channel (RC) are perturbed asymmetrically: as the ambient level grows, it scales the transmitted real scene multiplicatively while adding a see-through pedestal that washes out the perceived virtual image. This multiplicative-additive asymmetry turns ambient AR into a coupled two-channel color problem and complicates the seamless blending of virtual and real imagery, as well as their control through source power (sp) and screen transparency. Here, we develop a unified, device-independent two-channel color pipeline that jointly analyzes the virtual and real channels through CIELAB gamut evolution, transmitted-scene ΔE2000, and a chromatic-containment criterion on the a*b* plane, from which we derive a minimum source power map sp*(α, T) for the ambient level α and transparency T of the transparent screen (TS). A filter-parameter analysis confirms that an RGB-selective TS reduces the required sp by ∼30% relative to a spectrally flat TS at the practical daylight-like operating point of AR (T = 0.8, α = 1.0), while preserving a larger VC chromatic footprint with modest matched-throughput transmitted-scene distortion relative to an SF-TS (mean ΔE2000 ≤ 3 for T ≥ 0.8). Scene-level head-up display renderings further illustrate that the ambient-aware power schedule improves saturation and chromatic compatibility within the assumed face-gasket optical configuration. Taken together, our results establish the importance of two-channel color analysis that accounts for ambient light, the see-through screen, and the projection source.

We introduce nanoring scatterers with fixed outer and variable inner diameters as a method for achieving full-color transparent screen. Simulations show that these nanorings generate spectrally isolated RGB resonances with sub-30 nm linewidths and minimal crosstalk. Compared to nanodisks, they offer enhanced field confinement, reduced coupling, and stable spectral behavior under dense packing. Array-level analyses confirm that transparency is tunable via pitch adjustment without altering color balance. This spectral sharpening expands the perceived color gamut to similar to 120% under P3-D65 illumination, establishing nanorings as compact, fabrication-efficient elements for transparent projection screens.

For vivid, immersive overlay of virtual images onto background scenes in augmented reality (AR) applications, it is crucial for the display element to achieve controllability of spectral selectivity and transmittance level. At the current stage, the transmittance of self-emissive transparent displays is limited to at most ∼60 %, constrained by the fill factor of emissive regions, restricting their scalability for immersive experiences. Although projection-based transparent screens using frequency-selective scatterers offer a promising alternative, the platforms suffer from spectral broadening and instability originating from color-dependent scattering and inter-scatterer coupling. Here, we present a transparent screen architecture based on multicolor nanoring arrays. By tuning the nanoring’s resonance via inner-aperture size engineering, the architecture enables dense, symmetric RGB arrays with isolated and homogenized scattering responses. For inter-scatterer distances of 100–200+ nm, full-wave simulations confirm the robustness of well-isolated RGB reflections (FWHM < 25 nm), along with exceptional tunability of transmittance (50 % to above 80 %). As a platform for AR displays, we demonstrate the widest reported transparency-control range without any penalty to color balance or spectral selectivity. We also analyze the gamut area of projected images across transmittance levels, achieving a net gamut expansion (+11.0 % p at Λ = 120 nm; +5.5 % p at Λ = 190 nm) from the spectral narrowing of projection sources, and further propose a practical design map linking the maximum allowable transmittance to the ambient-to-source noise ratio. Our nanoring-based architecture provides a robust and scalable platform for next-generation transparent displays under real-world lighting conditions.

Ultrasound technology is widely utilized in applications, including tumor treatments, drug delivery, and skin care. However, improvements are required to prevent unwanted damage to non‐targeted tissues. The ultrasound focusing technology, represented by the highly intensive focused ultrasound (HIFU) technology, is actively researched to handle this problem. However, current technology is primarily limited in the point focusing of the ultrasound. Some applications, such as drug delivery and skin care, require 2D‐focusing of the ultrasound for effective utilization. Based on this necessity, this research proposes the rationally designed dodecagonal quasicrystal patterned (DQP) planar lens, which enables ultrasound focusing in 2D. The custom‐built ultrasound scanning setup confirms the 2D focusing behavior of the DQP lens. Furthermore, the developed DQP lens is integrated into the mobile ultrasound 2D focusing (MU2F) system and solved the bulkiness limitation of the HIFU system. The proposed MU2F system is applied in microneedle‐mediated drug delivery. The dramatic enhancement in the dissolution efficiency of the drug‐containing microneedle (≈2.5×) compared with the case without the MU2F system is confirmed. Through the proposed MU2F system, ultrasound‐based medical devices may widen their approachability from the clinic to the home.

The importance of the nanotransfer technique has been increased owing to its possibility in nanoscale mass-production, enabled by cost-effective and simply fabricable features. In this study, we developed a novel method for robust nanotransfer printing based on imidization-induced mechanical interlocking. The proposed imidization-induced nanotransfer printing (InTP) method enables various metal nanostructures to be easily transferred onto a polyimide substrate based on the mechanical interlocking force by using a controlled imidization process. The designed functional nanopatterns are transferred with high robustness. In addition, using a partial imidization process, we apply an additional adhesion force at the pattern-substrate interface to transfer materials with poor intrinsic adhesion, such as nickel, successfully. Owing to the exceptional robustness of the method, various 3D nanostructures, such as asymmetric sidewalls, suspended nanowires, and dual-layer line patterns, can be successfully transferred. Moreover, the InTP method was used to fabricate a uniform and high-temperature film heater and an asymmetric blind film.

Hierarchical structures allow one to improve device performance by exploiting the synergistic effects of micro/nano multiscale components. However, the structural complexity of hierarchical structures places limits on their fabrication and applications. Herein, a novel morphology-controllable wrinkled micro/nano hierarchical structure (WHS) was developed by integrating micropatterns, nanopatterns, and wrinkles on a single substrate to overcome these limitations. Each structure could be individually controlled, which offers unlimited design diversity. The produced WHS was used as a superhydrophobic triboelectric nanogenerator. Compared to a nanogenerator with on a film structure, the WHS-based nanogenerator showed a superior contact angle of 152.5°, which is indicative of high hydrophobicity, and an enhanced (by 608%) triboelectric effect, which was ascribed to the highly rough surface of the WHS. The WHS-based nanogenerator was used to fabricate a self-powered and water-repellent cough detection sensor with an entirely superhydrophobic structure and stable superior sensing performance during repeated water spraying.

In article number 1900997, Jun-Ho Jeong, Inkyu Park and co-workers introduce a novel method of electrothermal actuator (ETA) design, revealing that heterogeneous conductance control of ETA realizes locally shape-morphable actuation. The proposed actuator can be applied to soft robotics for handling various objects in diverse actuation shapes.

The development of soft electrothermal actuators (ETAs) that can be designed in arbitrary shapes and can easily handle soft objects has recently attracted much attention. However, the existing ETAs cannot be locally designed with a single substrate geometry, which places certain limitations on their applications. In addition, some limited materials (e.g., highly aligned carbon nanotubes) are used as heating layers for improving actuation controllability, which results in a high driving voltage, thus limiting the diversity and utility of ETAs. Herein, a novel method for a heterogeneous conductance-based locally shape-morphable electrothermal actuator (HC-ETA) is suggested, revealing that conductance programming allows control of the heat distribution in ETAs. Thus, by controlling the actuator heat distribution, the designed actuation motion can be implemented. Furthermore, Ag nanowire/carbon nanotube composites are used as conductive nanomaterials for a heating layer to realize a low-driving-voltage actuator. Additionally, combining a porous fabric substrate with a bipolymer actuator structure allows mechanical interlocking and the chemical bonding between actuator multilayers, resulting in significantly enhanced mechanical durability. Finally, the utility of the proposed actuator and the corresponding design method is successfully demonstrated by fabricating a biomimetic self-walking robot and an object lifting soft robot for vacuum chamber applications.

Many recently developed nanotransfer printing techniques have received much attention because of their simplicity and low cost. In addition, such techniques are suitable for fabricating nano/microscale sensors, optical elements, and electrical devices. However, conventional nanotransfer printing methods are time-consuming, cannot be easily used over large areas or with several different materials, and are not suitable for repeatedly transferring various materials onto the same substrate or a curved surface. Herein, a new nanotransfer printing method is introduced based on the oxidation of various metals and the formation of covalent bonds between spin- and spray-coatable adhesives and the chosen metal at low temperatures. These strong covalent bonds allow the fast transfer of the deposited materials from a polymer stamp without additional processing. A major advantage of this process is that it is metal-independent; nanowires of various metals are successfully transferred from the polymer stamp because strong covalent bonds form instantaneously between the metal and an adhesive-coated substrate. Moreover, this nanotransfer process can be used repeatedly to fabricate large-scale color filters from smaller areas of nanowires, regardless of the metal type and nanostructure orientation. Furthermore, plasmonic color filters composed of nanohole arrays can be obtained on both flat and curved surfaces.

Given the development of nano/microscale patterning techniques, efforts are being made to use them for fabricating metasurfaces. In particular, by using abrupt phase discontinuities, it is possible to generate holographic images from two-dimensional nanoscale-patterned metasurfaces. However, the fabrication of metasurface holograms is hindered by the high costs and long fabrication time involved, because the process requires expensive equipment such as that for electron-beam lithography. Therefore, it is difficult to realize metasurface holograms in a fast and repetitive manner. In this study, we propose a method for fabricating metasurface holograms based on the nanotransfer printing of the desired nanoscale patterns, which is assisted by Au nanoclusters, while controlling the bonding energy based on the shape of the deposited Au layer. Robust covalent bonds are formed between the Si of the adhesive used and the O of the SiO2 layer in order to transfer the deposited Au onto the transparent substrate quickly. It was found that the fabricated metasurface hologram coincides with the one designed by computer-generated holography. The proposed method should lead to a significant breakthrough in the fabrication of holograms based on different types of metasurfaces at a low cost in a fast, repetitive manner with various metals.

A novel method was developed for fabricating nanopatterns embedded on micropillar-structured surfaces using nanowelding technology for security identification. Commonly used substrates, that is, polyethylene films, glass wafers, Si wafers, and curved surfaces, were employed and their characteristics were evaluated. Cr was deposited onto the selected substrate to strengthen the adhesion force, and an adhesive layer of ultra-thin metal was deposited on top of the Cr layer. Lastly, nanopatterns were embedded on the substrates by nanowelding. The morphologies, cross sections, and three-dimensional (3D) images of the fabricated nanostructures were evaluated, and their crystalline structures and compositions were analyzed. Using the same method, nanopatterns embedded on micropillar-structured surfaces were fabricated for the first time as security patterns to improve security identification. The fabricated security patterns were characterized in three stages. First, micropillar structures and structural color were simply observed via optical microscopy to achieve a preliminary judgment. The appearance of structural color was due to the nanostructures fabricated on the micropillar surface. Next, the designed nanopatterns on the micropillar-structured surfaces were observed by scanning electron microscopy. Lastly, the changes in the spectral peaks were precisely observed using a spectrometer to achieve an enhanced security pattern. The fabricated security patterns can be suitable for valuable products, such as branded wines, watches, and bags. In addition, the proposed method offers a simple approach for transferring metal nanopatterns to common substrates. Moreover, the fabricated security patterns can have potential applications in semiconductor electrodes, transparent electrodes, and security identification codes.

A novel method was developed for fabricating nanopatterns embedded on micropillar-structured surfaces using nanowelding technology for security identification. Commonly used substrates, i.e., polyethylene film, glass wafer, Si wafer, and curved surface, were employed and their characteristics were evaluated. Cr was deposited onto the selected substrate to strengthen the adhesion force, and an adhesive layer of ultra-thin metal was deposited on top of the Cr layer. Lastly, nanopatterns were embedded on the substrates by nanowelding. The morphologies, cross-sections, and three-dimensional (3D) images of the fabricated nanostructures were evaluated, and their crystalline structures and compositions were analyzed. Using the same method, nanopatterns embedded on micropillar-structured surfaces were fabricated for the first time as security patterns to improve security identification. The fabricated security patterns were characterized in three stages. First, micropillar structures and structural color were simply observed via optical microscopy to achieve a preliminary judgment. The appearance of structural color was due to the nanostructures fabricated on the micropillar surface. Next, the designed nanopatterns on the micropillar-structured surfaces were observed by scanning electronic microscopy (SEM). Lastly, the changes in spectral peaks were precisely observed using a spectrometer to achieve an enhanced security pattern. The fabricated security patterns can be suitable for valuable products, such as branded wines, watches, and bags. In addition, the proposed method offers a simple approach for transferring metal nanopatterns to common substrates. Moreover, the fabricated security patterns can have potential applications in semiconductor electrodes, transparent electrodes, and security identification codes.

Organic-inorganic hybrid perovskite light-emitting diodes (PeLEDs) are promising for next-generation optoelectronic devices due to their potential to achieve high color purity, efficiency, and brightness. Although the external quantum efficiency (EQE) of PeLEDs has recently surpassed 20%, various strategies are being pursued to increase EQE further and reduce the EQE gap compared to other LED technologies. A key point to further boost EQE of PeLEDs is linked to the high refractive index of the perovskite emissive layer, leading to optical losses of more than 70% of emitted photons. Here, it is demonstrated that a randomly distributed nanohole array with high-index contrast can effectively enhance outcoupling efficiency in PeLEDs. Based on a comprehensive optical analysis on the perovskite thin film and outcoupling structure, it is confirmed that the nanohole array effectively distributes light into the substrate for improved outcoupling, allowing for 1.64 times higher light extraction. As a result, highly efficient red/near-infrared PeLEDs with a peak EQE of 14.6% are demonstrated.

The increasing demand for smart fabrics has inspired extensive research in the field of nanomaterial-based wearable heaters. However, existing stretchable heaters employ polymer substrates, and hence require additional substrate-fabric bonding that can result in high thermal contact resistance. Moreover, currently used stretchable fabric heaters suffer from high sheet resistance and require complex fabrication processes. In addition, conventional fabrication methods do not allow for patternability, thus hindering the fabrication of wearable heaters with diverse designs. Herein, we propose an improved spray coating method well suited for the preparation of patternable heaters on commercial fabrics, combining the structural stability of carbon nanotubes with the high electrical conductivity of Ag nanowires to fabricate a stretchable fabric heater with excellent mechanical (stretchability ≈ 50%) and electrical (sheet resistance ≈ 22 Ω sq-1) properties. The fabricated wearable heater reaches typical operating temperatures of 35 °C-55 °C at a low driving voltage of 3-5 V with a proper surface power density of 26.6-72.2 [Formula: see text] (heater area: [Formula: see text]) and maintains a stable heating temperature for more than 30 h. This heater shows a stable performance even when folded or rolled, thus being well suited for the practical wearable applications.

In this study, 8 in. wafer-scale flexible polarization-dependent color filters with Ag-TiO2 composite nanowires have been fabricated using nanoimprint and E-beam evaporation. The filters change their color via a simple rotation of the polarizer. In addition, the color of the filter can be controlled by altering the thickness of the Ag and TiO2 nanowires deposited on the polymer patterns. Polarization-dependent color filters were realized by selective inhibition of transmission using the plasmonic resonance at the insulator/metal/insulator nanostructure interface, which occurs at particular wavelengths for the transverse magnetic polarizations. Special colors, including purple, blue, green, yellow, and pink, could be obtained with high transmission beyond 65% by varying the thickness of the deposited Ag and TiO2 nanowires on the periodic polymer pattern under transverse magnetic polarization. In addition, a continuous color change was achieved by varying the polarization angle. Last, numerical simulations were implemented in comparison with the experimental results, and the mechanism was explained. We believe that this simple and cost-effective method can be applied to processes such as anticounterfeiting and holographic imaging as well as to color displays.

Recently, metasurfaces composed of artificially fabricated subwavelength structures have shown remarkable potential for the manipulation of light with unprecedented functionality. Here, we first demonstrate a metasurface application to realize a compact near-eye display system for augmented reality with a wide field of view. A key component is a see-through metalens with an anisotropic response, a high numerical aperture with a large aperture, and broadband characteristics. By virtue of these high-performance features, the metalens can overcome the existing bottleneck imposed by the narrow field of view and bulkiness of current systems, which hinders their usability and further development. Experimental demonstrations with a nanoimprinted large-area see-through metalens are reported, showing full-color imaging with a wide field of view and feasibility of mass production. This work on novel metasurface applications shows great potential for the development of optical display systems for future consumer electronics and computer vision applications.