Smart adhesives with engineered mechanical structures have emerged as a transformative technology with broad applications in fields such as wearable healthcare devices, bioengineering, and soft robotics. By integrating advanced mechanical architectures like kirigami, tessellations, and multilayered designs, these adhesives exhibit enhanced surface and mechanical properties that lead to superior interfacial adhesion. Such designs offer critical advantages—improved stretchability, substrate conformability, and increased adhesion strength—over conventional adhesives. This review explores the range of engineered structures used in smart adhesives and demonstrates how these innovations address the limitations of traditional adhesives. Additionally, we discuss their applications in wearable healthcare devices, flexible electronics, and robotics.

The current research explores a facile two-step method for fabricating flexible RGO-decorated MnO2 2 nanorod electrodes on a carbon cloth substrate, ideal for wearable energy storage devices. The strategy involves first depositing MnO2 2 nanorods on the carbon cloth utilizing a hydrothermal technique, followed by a simple ex-situ decoration with reduced graphene oxide by varying concentrations. Through comprehensive physical and electrochemical analyses, the impact of different concentrations of graphene oxide on the physical and electrochemical characteristics of MnO2 2 electrodes is thoroughly examined. Among the investigated concentrations of graphene oxide, the RGO-decorated MnO2 2 electrode featuring a 20 mg/100ml concentration of graphene oxide showcased the maximum specific capacitance reaching 1072.28 F/g at a 5 mV/sec in a 1M Na2SO4 2 SO 4 electrolyte. Furthermore, this electrode demonstrated commendable long-term cycle stability, preserving over 87% of its original capacitance after enduring 2000 cycles of charge and discharge. A symmetric prototype supercapacitor device has been constructed to assess their practical utility utilizing symmetric electrodes and an aqueous electrolyte. This symmetric device exhibits promising electrochemical properties, underscoring the potential of the developed electrodes for real-world implementation. The remarkable structural, morphological, and electrochemical characteristic attributes of RGO-decorated MnO2 2 nanorods grown on the carbon cloth substrate position them as superior electrode materials tailored for the burgeoning realm of wearable energy storage devices, paving the way for advanced flexible and efficient energy storage solutions.

We present an azimuthal-rotation-controlled dynamic nanoinscribing (ARC-DNI) process for continuous and scalable fabrication of asymmetric nanograting structures with tunable periods and shape profiles. A sliced edge of a nanograting mold, which typically has a rectangular grating profile, slides over a polymeric substrate to induce its burr-free plastic deformation into a linear nanopattern. During this continuous nanoinscribing process, the “azimuthal angle,” that is, the angle between the moving direction of the polymeric substrate and the mold’s grating line orientation, can be controlled to tailor the period, geometrical shape, and profile of the inscribed nanopatterns. By modulating the azimuthal angle, along with other important ARC-DNI parameters such as temperature, force, and inscribing speed, we demonstrate that the mold-opening profile and temperature- and time-dependent viscoelastic polymer reflow can be controlled to fabricate asymmetric, blazed, and slanted nanogratings that have diverse geometrical profiles such as trapezoidal, triangular, and parallelogrammatic. Finally, period- and profile-tunable ARC-DNI can be utilized for the practical fabrication of diverse optical devices, as is exemplified by asymmetric diffractive optical elements in this study.

We demonstrate flexible transmissive structural color filters with enhanced color purity and brightness by exploiting resonance overlap within multiple cavities in penta-layered structures. Using an inverse design method that combines optimization and exhaustive search algorithms, the material choices and layer thicknesses are determined through a loss function based on the CIE XYZ color space, optimizing both color purity and brightness. The resulting color gamut is comparable to standard RGB, as assessed in the CIE xy color space, with luminance (Y from CIE 1931 model) values for the fabricated transmissive RGB colors being 0.14, 0.51, and 0.14. The contribution of each cavity is thoroughly analyzed using optical admittance diagrams and resonant mode calculations. Furthermore, the transmissive colors on a flexible substrate exhibit excellent durability, retaining consistent transmission efficiency and color purity even after 4,000 bending cycles and performing reliably at a bending radius of 5 mm. The versatility of this design approach makes them suitable for a wide range of applications, including e-paper displays, image sensors, flexible wavelength-selective optoelectronic devices, and decorations.

This article describes the automatic spray pyrolysis deposition (ASPD) process for the synthesis of hierarchically structured 3D nanoporous vanadium oxide (V2O5) transparent material on a fluorine-doped tin oxide (FTO) substrate. The deposition of material occurs at 673 K using an aqueous solution of NH4VO3, with a constant solution spray rate of 10 mL min-1 and airflow rate of 10 L min-1. Structural analysis confirms the pure orthorhombic structure formation of the V2O5 material, while FE-SEM images show a well-organized 3D spongy-like porous architecture. The excellent conformality of the ASPD enables the deposition of high-aspect-ratio 3D structured nanoporous V2O5 electrodes for next-generation supercapacitor applications. The hierarchical structured 3D nanoporous V2O5 electrode exhibits superior electrochemical performance in a 1M Na2SO3 electrolyte. Within the potential window 0 to -1.3 V, the electrode archives the highest specific capacitance (SC) of 453.32 F g-1 and also retains 86% of its capacitance after 5000 cycles. These properties mainly originate from the crystallinity, 3D nanoporous structure, and fast and easy ionic intercalation through the material. Furthermore, a symmetric supercapacitor device using this electrode is fabricated and which yields outstanding electrochemical performance. Overall, the results highlight the potential of 3D nanoporous V2O5 as an outstanding electrode material for next-generation supercapacitor applications. Graphical illustration of electrochemical charging-discharging behavior and possible reaction on vanadium oxide electrode for next-generation supercapacitor application.image

We demonstrate the facile fabrication of flexible and transparent heating structures via the soft-contact printing and patterning (SCOP) of an ionic metal solution layer, a process generally applicable to flat, flexible, and curved surfaces with scalable sizes. The SCOP process involves the conformal contact of a soft micropattern mold onto an ionic metal solution and mild thermal annealing under controlled temperature and pressure conditions to reduce metal ions into a micropatterned metallic structure. Through parametric optimization of the SCOP pressure and annealing temperature, multilayering with sequential SCOP processes, and airbrush coating of a carbon nanotube solution, a printable metallic micropattern can be tailored to a high-performance transparent heater capable of achieving the temperature up to 125 °C at 8 V and optical transmittance of 80

We present quad-layered structural color filters producing transmissive red (R), green (G), and blue (B) colors with high brightness and high purity, where thicknesses of layers for the RGB colors are optimized by using a L-BFGS-B algorithm. To evaluate the performance of the proposed structural color filters, computer-based inverse designs based on meta-heuristic and reinforcement learning algorithms are employed, where the optical properties obtained from the inverse designs are comparable to those shown in our proposed design. A peak separation phenomenon in dual cavities is applied to make a spectral response rectangular, and also a resonance order is optimally tailored to maximize the transmittance at a resonant wavelength with the suppression of undesired higher-order resonances at the same time for achieving pure colors. Transmission efficiency over 75% and the full width at half-maximum (FWHM) less than 90 nm are achieved. Besides, selecting a cavity medium with a high refractive index allows the optical properties of the structural color filters to remain almost constant in wavelength over a broad range of incident angles up to 60°. Moreover, only a few deposition steps are necessary, thus leading to a much simple fabrication as compared to previous works that involve a series of complicated lithographic processes. The approach described in this study may provide new ways for achieving diverse applications, such as displays, imaging devices, decorations, and colored solar cells.

The current research explores a facile two-step method for fabricating flexible RGO-decorated MnO2 nanorod electrodes on a carbon cloth substrate, ideal for wearable energy storage devices. The strategy involves first depositing MnO2 nanorods on the carbon cloth utilizing a hydrothermal technique, followed by a simple ex-situ decoration with reduced graphene oxide by varying concentrations. Through comprehensive physical and electrochemical analyses, the impact of different concentrations of graphene oxide on the physical and electrochemical characteristics of MnO2 electrodes is thoroughly examined. Among the investigated concentrations of graphene oxide, the RGO-decorated MnO2 electrode featuring a 20 mg/100ml concentration of graphene oxide showcased the maximum specific capacitance reaching 1072.28 F/g at a 5 mV/sec in a 1M Na2SO4 electrolyte. Furthermore, this electrode demonstrated commendable long-term cycle stability, preserving over 87% of its original capacitance after enduring 2000 cycles of charge and discharge. A symmetric prototype supercapacitor device has been constructed to assess their practical utility utilizing symmetric electrodes and an aqueous electrolyte. This symmetric device exhibits promising electrochemical properties, underscoring the potential of the developed electrodes for real-world implementation. The remarkable structural, morphological, and electrochemical characteristic attributes of RGO-decorated MnO2 nanorods grown on the carbon cloth substrate position them as superior electrode materials tailored for the burgeoning realm of wearable energy storage devices, paving the way for advanced flexible and efficient energy storage solutions.

Solvent-mediated spray pyrolysis (SMSP) is recognized as a flexible method for fabricating a variety of nanomaterials, such as 2D vanadium oxide nanostructures. This process involves atomizing a precursor solution onto a hot surface, leading to the evaporation of the solvent and decay of the precursor, culminating in the development of the target nanomaterial. The inclusion of a solvent in SMSP enhances the ability to tailor the morphology and size of nanostructures and facilitates the creation of nanomaterials on diverse substrates. The current research utilized SMSP to produce 2D vanadium oxide nanostructures aimed at advanced energy storage applications. A 0.05 M solution of ammonium metavanadate (NH4VO3) in 50 ml of various solvents, including methanol, ethanol, and propanol was prepared. This solution was then sprayed onto a preheated stainless-steel substrate (673 K) using an automated spray nozzle, with compressed air serving as the carrier gas at a rate of 10 L/min. The solution flow rate was consistently held at 10 ml/min, and the optimal distance between the nozzle and substrate was determined to be 30 cm. Characterization of the resulting 2D vanadium oxide nanostructures underwent multiple physical and electrochemical techniques. The XRD results confirmed the formation of a tetragonal crystalline structure. The SEM/TEM images revealed nanostructures with a rectangular plate-like morphology with an average 13.24 nm thickness. Electrochemical evaluation was conducted by a standard three-electrode system in a 1 M Na2SO3 electrolyte, where the nanostructures synthesized with methanol solvent demonstrated a superior specific capacitance of 721.28 F/g at a 5 mV/s scan rate as compared to those synthesized with other solvents. Additionally, these nanostructures retain over 90 % of their initial capacitance after 3000 charge-discharge cycles. The remarkable specific capacitance and durability through numerous cycles highlight the potential of those 2D vanadium oxide nanostructures as promising candidates for electrodes in high-performance energy storage devices.

We demonstrate the all-solution-based fabrication of metal-nanodot-decorated semiconductor nanorod structures, with the entire process performable at very low or room temperatures. On the surfaces of semiconducting ZnO nanorods (ZNRs) hydrothermally grown on a solution-processed Ag layer at 90 degrees C, Ag nanodots are reduced from Ag cations in an ionic solution at room temperature by taking UV-induced electrons from ZNRs. Ag nanodots can be deposited at a specific position (top, bottom, or whole region) of the ZNRs by using a controlled ionic Ag solution coating method. We investigate the UV-assisted room-temperature photoreduction (RTPR) mechanism by focusing on the roles of ZnO and solvent. We further examine that the size, density, and spatial distribution of Ag nanodots can be controlled by regulating the concentration of the ionic Ag solution and RTPR time. The resulting hybrid Ag/ZNR architecture, processable on a large-area flexible substrate, exhibits significantly enhanced photocurrent level, responsivity, and selectivity for the incident UV light due to the localized surface plasmon resonance of the Ag nanodots and rapid electron transfer across the Ag/ZnO interface. Our all-solution-based room-temperature approach offers an environmentally sustainable, low-cost, and scalable method for the design and fabrication of metal-nanodot-decorated semiconductor nanostructures applicable to optoelectronic transducers and many other applications.

We demonstrate the facile fabrication of metal-wire-embedded microtrenches interconnected with semiconducting ZnO nanowires (ZNWs) through the continuous mechanical machining of micrograting trenches, the mechanical embedding of solution-processable metal wires therein, and the metal-mediated hydrothermal growth of ZNWs selectively thereto. The entire process can be performed at room or a very low temperature without resorting to vacuum, lithography, and etching steps, thereby enabling the use of flexible polymer substrates of scalable sizes. We optimize the fabrication procedure and resulting structural characteristics of this nanowire-interconnected flexible trench-embedded electrode (NIFTEE) architecture. Specifically, we carefully sequence the coating, baking, and doctor-blading of an ionic metal solution for the embedding of clean metal wires, and control the temperature and time of the hydrothermal ZNW growth process for faithful interconnections of such trench-embedded metal wires via high-density ZNWs. The NIFTEE structure can function as a bending-sensitive optoelectronic sensor, as the number of ZNWs interconnecting the neighboring metal wires changes upon mechanical bending. It may benefit further potential applications in diverse fields such as wearable technology, structural health monitoring, and soft robotics, where bending-sensitive devices are in high demand.

AbstractWe present quad-layered reflective structural color filters generating vivid additive primary colors by controlling a mode number in a Fabry–Perot (FP) cavity and an anti-reflective (AR) coating layer, thus accomplishing high spectral contrast which is highly demanded in creating sharp colors. The reflection brightness of fabricated structural color filters is over 78% and a color gamut is comparable to the standard color gamut (sRGB). Higher-order resonant modes are exploited yielding a narrow passband with strong suppression of the reflection at shorter and longer wavelength ranges for a green color, while red and blue colors are produced by employing fundamental resonant modes. Besides, the structural color filters maintain both high brightness and high color purity at oblique incidence angles up to 40° due to a small angle of refraction by a cavity medium with high refractive index. Moreover, a large-scale fabrication is enabled owing to the simplicity of a device structure, where thin film deposition is used. The scheme presented in this work may open the door to a number of applications, such as reflective displays, imaging devices, colored photovoltaics, and decorations.

Flexible transparent electrodes (FTEs) are essential for advancing flexible electronics, energy systems, and biomedical devices. Conventional FTEs, which use silver nanowire coatings on flexible substrates, face limitations due to poor oxidation resistance and difficulties in forming reliable mechanical and electrical interconnections with other device components. In this study, we propose a versatile FTE design that integrates Ag-Au core-shell nanowires and self-adhesive microstructures into a regular grid pattern. This electrode exhibits robust self-adhesion, enabling precise mechanical and electrical contacts across various substrates without additional adhesives. The optical and electrical properties can be finely tuned by manipulating the microstructures and nanowire coatings. Notably, the electrode demonstrates remarkable oxidation resistance, even under exposure to oxidizing agents, elevated temperatures, and high-humidity environments. Our findings provide practical pathways for implementing FTEs in a wide range of emerging optoelectronic devices, leveraging their exceptional chemical and thermal stability.

Metasurfaces, composed of periodic nanostructures, have been attractive because of their extraordinary modulation of light propagation. However, conventional electron-beam lithography to fabricate metasurfaces is time-consuming and costly, which prevents commercialization of functional metasurfaces. We investigate nanoimprint lithography-based technique for single-step fabrication of metasurfaces. A high-refractive-index material is granulated and mixed with nanoimprint resin. This mixture results in higher effective refractive index, and thus can be utilized to directly fabricate metasurfaces. Besides, diverse processing conditions are investigated such as swelling effect for the successful replication of high-aspect-ratio nanostructures. Finally, we verify the optimized nanoparticle-embedded resin printing process through the replication of metasurfaces with various dimensions and an optimal design.

Herein, Manganese dioxide (MnO2) electrode material with a unique morphology was synthesized using low cost, one-step hydrothermal method on flexible carbon cloth substrate. For detail understanding the influence of deposition parameters on the electrochemical performance of MnO2 electrode material, we have synthesized MnO2 at different deposition parameters like deposition time and concentration of precursor solution. The structural, morphological, and surface area properties of the as-synthesized MnO2 nanostructures electrodes deposited at different deposition time as well as different precursor concentration have been systematically characterized by using different physical and electrochemical characterization techniques. The SEM micrographs show different morphologies like nanothorn, nanourchins and naoflowers at concerning deposition time and precursor concentration. Among all the electrodes nanourchin-like MnO2 nanostructures deposited using 0.005 M precursor concentration for 8 h at 160 degrees C shows the highest specific capacitance value of 470.46 F/g at a scan rate of 5 mV/s and good cycling stability after 5000 cycles. For practical application purpose, a symmetric prototype supercapacitor device has been fabricated by using solid-state gel polymer electrolyte. The symmetric device shows good electrochemical performance. Overall results show that nanourchin-like MnO2 grown on carbon cloth substrate is potential electrode material for practical application for energy storage.

Understanding optical interference in multilayer structures is of critical importance for designing a variety of optical coatings that have been widely used as an essential element in diverse applications. We demonstrate that the transition of reflective properties from a valley to a peak occurs by a metal on the incident side in a cavity structure comprising a transparent dielectric medium surrounded by two metals. The reflected light destructively interferes giving rise to a reflection dip when there is a large difference between the refractive index and the extinction coefficient of the metal, whereas a constructive interference occurs with the refractive index that is comparable to the extinction coefficient yielding a reflection peak. In addition, an admittance and an electric field distribution of the cavity structure are investigated with different constituent metals. Our results described in this paper provides a better understanding of the fundamental principles of the optical cavity, thereby potentially extending the range of possible future applications.

We demonstrate continuous fabrication of flexible transducer devices consisting of interdigitated (IDT) Ag microelectrodes interconnected by ZnO nanowires (ZNWs), created via serially connected solution-processable micro- and nanofabrication processes. On an Ag layer obtainable from the mild thermal reduction of an ionic Ag ink coating, the roll-to-roll-driven photolithography process [termed photo roll lithography (PRL)] followed by wet-etching can be applied to continuously define the IDT microelectrode structure. Conformal ZNWs can then be grown selectively on the Ag electrodes to interconnect them via an Ag-mediated hydrothermal ZNW growth that does not require high-temperature seed sintering. Given that all of these constitutive processes are vacuum-free and solution-processable at a low temperature, and are compatible with continuous processing onto flexible substrates, they can be eventually configured into the roll-to-roll-processable progressive assembly. Through parametric optimizations of processes consisting of the roll-to-roll-configurable, solution-based progressive assembly of nanostructures (ROLSPAN), a flexible transducer consisting of ZNW-interconnected, PRL-ed IDT Ag electrodes can be developed. This flexible architecture faithfully performs UV sensing as well as optoelectronic transduction. The ROLSPAN concept along with its specific applicability to flexible devices may inspire many diverse functional systems requiring high-throughput low-temperature fabrication over large-area flexible substrates.

Fabricating high‐quality thin films on a 3D structured polymer substrate is crucial in realizing high‐performance flexible electronics. Herein, simple yet effective twofold strategies are demonstrated to directly fabricate flexible thin film capacitors on polymer substrate: the crystallization of high‐ k TiO 2 film by plasma‐assisted atomic layer annealing at low temperature (80 °C) on nanostructured polycarbonate (PC) substrates fabricated by simple dynamic nanoinscribing (DNI) technique. Plasma‐induced amorphous‐to‐anatase phase transformation occurs in PEALD TiO 2 /ZrO 2 bilayer thin films, resulting in the capacitance density increase by 30%. The DNI patterning of PC substrates in two directions further increases the surface area by 35% and the capacitance density by 37%, leading to the flexible capacitor of a record‐high capacitance density (24.2 nF mm −2 ) with mechanical stability.

In this report, we present a straightforward method for bridging a nanoplasmonic sensor with a conventional plate reader. By attaching lithographically prepared plasmonic nanostructures to a commercially available microwell strip, which has a perforated bottom, we could measure highly sensitive optical signals of plasmonic nanostructures using a conventional plate reader. The absorbance measurements and electromagnetic simulations show that a proper alignment between light polarization and the plasmonic nanostructure improves the sensing performance, which can be achieved with a linear polarizing film. Furthermore, the multiplexed detection capability of the proposed nanoplasmonic sensor chip was successfully demonstrated by monitoring four different enzyme–substrate reactions. These results illustrate the potential of the proposed nanoplasmonic sensor chip, which can combine advanced nanoplasmonic sensors with the well-developed microwell plate reader.