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This paper presents a novel approach for fabricating porous NiO films decorated with nanowires, achieved through sputtering followed by thermal oxidation of a metallic layer. Notably, we successfully fabricate NiO nanowires using this simple and cost-effective method, demonstrating its potential applicability in the gas-sensing field. Furthermore, by using the film of our nanowires, we are able to easily prepare NiO sensors and deposit the required Pt electrodes directly on the film. This is a key advantage, as it simplifies the fabrication process and makes it easier to integrate the sensors into practical gas-sensing devices without the need for nanostructure transfer or intricate setups. Scanning electron microscopy (SEM) reveals the porous structure and nanowire formation, while X-ray diffraction (XRD) confirms the presence of the NiO phase. As a preliminary investigation, the gas-sensing properties of NiO films with varying thicknesses were evaluated at different operating temperatures. The results indicate that thinner layers exhibit superior performances. Gas measurements confirm the p-type nature of the NiO samples, with sensors showing high responsiveness and selectivity toward NO2 at an optimal temperature of 200 °C. However, incomplete recovery is observed due to the high binding energy of NO2 molecules. At higher temperatures, sufficient activation energy enables a full sensor recovery but with reduced response. The paper discusses the adsorption–desorption reaction mechanisms on the NiO surface, examines how moisture impacts the enhanced responsiveness of Pt-NiO (2700%) and Au-NiO (400%) sensors, and highlights the successful fabrication of NiO nanowires through a simple and cost-effective method, presenting a promising alternative to more complex approaches.

The increasing significance of hydrogen (H 2 ) gas as a clean energy source has prompted the development of high-performance H 2 gas sensors. Palladium (Pd)-based sensors, with their advantages of selectivity, scalability, and cost-effectiveness, have shown promise in this regard. However, the long-term stability and reliability of Pd-based sensors remain a challenge. This study not only identifies the exact cause for performance degradation in palladium (Pd) nanowire H 2 sensors, but also implements and optimizes a cost-effective recovery method. The results from density functional theory (DFT) calculations and material analysis confirm the presence of C = O bonds, indicating performance degradation due to carbon dioxide (CO 2 ) accumulation on the Pd surface. Based on the molecular behavior calculation in high temperatures, we optimized the thermal treatment method of 200 °C for 10 minutes to remove the C = O contaminants, resulting in nearly 100% recovery of the sensor’s initial performance even after 2 months of contamination. Retaining sensor performance with long-term use is highly challenging. Here, the authors refined the thermal recovery method in Pd nanowire H 2 sensors, effectively removing C = O surface contaminants to ensure long-term stability.

Recently, copper oxide (CuO)-based visible-light photodetectors have attracted great interest due to their narrow bandgap (1.2 eV), low cost, and ease of fabrication. However, there has been insufficient theoretical analysis and study of CuO-based photodetectors, resulting in inferior performance in terms of responsivity, detectivity, and response speed. This work develops a method to enhance the performance of CuO photodetectors by engineering a grain structure based on a newly-developed theoretical model. In the developed theoretical grain-structure model, the grain size and the connections between grains are considered because they can strongly affect the optoelectronic characteristics of CuO photodetectors. Based upon the proposed model, the engineered CuO device achieves enhanced optoelectronic performance. The engineered device shows high responsivity of 15.3 A/W and detectivity of 1.08 × 10 11 Jones, which are 18 and 50 times better than those of the unoptimized device, and also shows fast rising and decaying response speeds of 0.682 s and 1.77 s, respectively. In addition, the proposed method is suitable for the mass-production of performance-enhanced, reliable photodetectors. By using a conventional semiconductor fabrication process, a photodetector-array is demonstrated on a 4-inch wafer. The fabricated devices show uniform, high, and stable optoelectronic performance for a month.

Pressure sensors provide intuitive and easy-to-use information, making them essential for Human-Machine Interface (HMI) applications. However, capacitive pressure sensors, although prevalent in industrial applications, suffer from critical vulnerabilities to external interferences like water droplets and proximity. Without addressing these issues, pressure sensors can never be effectively utilized in various real-world applications. This paper addresses this critical issue by identifying fringe fields as the primary cause of interference and proposing a nanogap structured capacitive pressure sensor. By reducing the electrode gaps to hundreds of nanometers, our sensor effectively mitigates fringe field effects, ensuring reliable pressure detection and high spatial resolution. We demonstrate the sensor’s capabilities through wireless applications such as an artificial pressure sensing system and a force touch pad system, both showcasing exceptional resilience and accuracy. This innovation paves the way for robust, interference-free pressure sensors, significantly advancing HMI technology. The authors use a nanogap structure in capacitive pressure sensors to suppress fringe fields, the cause of interference. This enables interference-free operation while achieving high resolution and bending insensitivity for human-machine interface applications.

Recently, copper oxide (CuO) has drawn much attention as a promising material in visible light photodetection with its advantages in ease of nanofabrication. CuO allows a variety of nanostructures to be explored to enhance the optoelectrical performance such as photogenerated carriers scattering and bandgap engineering. However, previous researches neglect in-depth analysis of CuO’s light interaction effects, restrictively using random orientation such as randomly arranged nanowires, single nanowires, and dispersed nanoparticles. Here, we demonstrate an ultra-high performance CuO visible light photodetector utilizing perfectly-aligned nanowire array structures. CuO nanowires with 300 nm-width critical dimension suppressed carrier transport in the dark state and enhanced the conversion of photons to carriers; additionally, the aligned arrangement of the nanowires with designed geometry improved the light absorption by means of the constructive interference effect. The proposed nanostructures provide advantages in terms of dark current, photocurrent, and response time, showing unprecedentedly high (state-of-the-art) optoelectronic performance, including high values of sensitivity ( S  = 172.21%), photo-responsivity ( R  = 16.03 A/W, λ = 535 nm), photo-detectivity ( D *  = 7.78 × 10 11 Jones), rise/decay time ( τ r / τ d  = 0.31 s/1.21 s).

With the exponential growth of the semiconductor industry, radiation-hardness has become an indispensable property of memory devices. However, implementation of radiation-hardened semiconductor memory devices inevitably requires various radiation-hardening technologies from the layout level to the system level, and such technologies incur a significant energy overhead. Thus, there is a growing demand for emerging memory devices that are energy-efficient and intrinsically radiation-hard. Here, we report a nanoelectromechanical non-volatile memory (NEM-NVM) with an ultra-low energy consumption and radiation-hardness. To achieve an ultra-low operating energy of less than 10 fJ bit − 1 , we introduce an out-of-plane electrode configuration and electrothermal erase operation. These approaches enable the NEM-NVM to be programmed with an ultra-low energy of 2.83 fJ bit − 1 . Furthermore, due to its mechanically operating mechanisms and radiation-robust structural material, the NEM-NVM retains its superb characteristics without radiation-induced degradation such as increased leakage current, threshold voltage shift, and unintended bit-flip even after 1 Mrad irradiation. Achieving both low energy consumption and radiation-hardness is highly challenging in memory devices. Here, the authors demonstrate a sub-10 fJ/bit, radiation-hard nanoelectromechanical non-volatile memory through structural and material approaches.

An infrared (IR) absorber is a crucial component for thermal detectors, requiring high absorptance over a broad wavelength range while maintaining low heat capacity for optimal performance. Most thermal detectors use a thin film IR absorber that is suspended in air, supported by a layer beneath it for mechanical stability. However, this support layer increases heat capacity without contributing to IR absorptance, thereby reducing the performance of thermal detectors. In this paper, we introduce a polarization-independent nanowire array absorber using flanged nanowires with a C-shaped cross-section. This C-shaped design provides mechanical stability, eliminating the need for a support layer. Although nanowire array is generally known to exhibit polarization characteristics, the unique structure of the proposed flanged nanowires enables them to achieve polarization-independent properties, resulting in high absorptance similar to that of film absorbers. We theoretically analyzed the polarization-independent characteristics of the flanged nanowires using an optical circuit model and optimized the flanged nanowire structure using finite-difference time-domain (FDTD) simulations. Finally, we experimentally demonstrated the polarization-independent characteristics of the flanged nanowires and confirmed their high absorptance comparable to that of film absorbers.

Antireflection, vital in optoelectronics devices such as solar cells and photodetectors, reduces light reflection and increases absorption. Antireflective structures (ARS), a primary method by which to realize this effect, control the refractive index (RI) profile based on their shape. The antireflection efficiency depends on the refractive index profile, with the quintic RI profile being recognized as ideal for superior antireflection. However, fabricating nano-sized structures with a desired shape, particularly in silicon with a quintic RI profile, has been a challenge. In this study, we introduce a funnel-shaped silicon (Si) ARS with a quintic RI profile. Its antireflective properties are demonstrated through reflectance measurements and by an application to a photodetector surface. Compared to the film Si and cone-shaped ARS types, which are common structures to achieve antireflection, the funnel-shaped ARS showed reflectance of 4.24% at 760 nm, whereas those of the film Si and cone-shaped ARS were 32.8% and 10.6%, respectively. Photodetectors with the funnel-shaped ARS showed responsivity of 0.077 A/W at 950 nm, which is 19.54 times higher than that with the film Si and 2.45 times higher than that with the cone-shaped ARS.

Miniaturized fluorescence imaging systems are promising platforms that overcome the limited use of conventional microscopes in the biomedical field. However, there are physical limitations for multicolor fluorescence imaging in existing miniaturized imaging systems because multiple filters have to be integrated into a small structure. Here, we present a miniaturized multicolor fluorescence imaging system integrated with single polydimethylsiloxane (PDMS) light-guide plate (LGP) for multicolor fluorescence imaging. The PDMS LGP allows guiding the transmitted light from the light source only to the fluorescent samples regardless of the wavelength of the light source. Thus, our system is capable of multicolor fluorescence imaging without multiple filters that block the excitation light. We demonstrated the usability of our system in the biomedical field by observing green- and red-labeled cells in the incubator. Our proposed system can be used in a wide range of applications for studies that require multicolor fluorescence imaging in the biomedical field.

Multimodal neural interfaces open new opportunities in brain research by enabling more sophisticated and systematic neural circuit dissection. Integrating complementary features across distinct functional domains, these multifunctional neural probes have greatly advanced the interrogation of complex neural circuitry. However, introducing multiple functionalities into a compact form factor for freely behaving animals presents substantial design hurdles that complicate the device or require more than one device. Moreover, fixed functionality poses challenges in meeting the dynamic needs of chronic neuroscience inquiry, such as replacing consumable parts like batteries or drugs. To address these limitations, the modular implantable neural device (MIND) is introduced with a one‐touch magnetic assembly mechanism. Leveraging the seamless exchange of neural interface modules such as optical stimulation, drug delivery, and electrical stimulation, MIND ensures functional adaptability, reusability, and scalability. The versatile design of MIND will facilitate brain research by enabling simplified access to multiple functional modalities as needed. The modular implantable neural device (MIND) features a one‐touch magnetic assembly mechanism for seamless exchange of neural interface modules, including optical stimulation, drug delivery, and electrical stimulation. Designed for functional adaptability, reusability, and scalability, MIND overcomes the challenges of fixed functionality neural devices, facilitating advanced, flexible neuroscience research in freely behaving animals with simplified access to multiple modalities.