npj Flexible Electronics最新文献

Increasing the proximity of microelectrode arrays (MEA) to targeted neural tissues can establish efficient neural interfaces for both recording and stimulation applications. This has been achieved by constructing protruding three-dimensional (3D) structures on top of conventional planar microelectrodes via additional micromachining steps. However, this approach adds fabrication complexities and limits the 3D structures to certain shapes. We propose a one-step fabrication of MEAs with versatile microscopic 3D structures via “microelectrothermoforming (μETF)” of thermoplastics, by utilizing 3D-printed molds to locally deform planar MEAs into protruding and recessing shapes. Electromechanical optimization enabled a 3D MEA with 80 μm protrusions and/or recession for 100 μm diameter. Its simple and versatile shaping capabilities are demonstrated by diverse 3D structures on a single MEA. The benefits of 3D MEA are evaluated in retinal stimulation through numerical simulations and ex vivo experiments, confirming a threshold lowered by 1.7 times and spatial resolution enhanced by 2.2 times.

Electro-Spun nanofibers (ESNs), with their design flexibility, tailorable morphologies, and high surface area, are well-favored as triboelectric nanogenerator (TENG) materials for wearable electronics. Here, various aspects of ESNs-based wearable TENGs were examined. After introducing the most common TENG operating modes, an insightful overview of wearable TENG applications based on ESNs was presented. In this survey, a special attention is paid to wearable sensing, human-machine interaction, self-powered devices, and amplified energy harvesting. Efforts towards improving energy conversion efficiency, material durability, and compatibility with diverse wearable platforms were visited. Finally, a perspective based on particularly material aspect of ESNs is given, which could be insightful in tackling prevailing challenges and giving birth to new directions.

Flexible integrated circuits (FlexICs) have drawn increasing attention, particularly in remote sensors and wearables operating in a limited power budget. Here, we present an ultra-low power timer designed to wake-up an external circuit periodically, from a deep-sleep state into an active state, thereby largely reducing the system power consumption. We achieved this with a circuit topology that exploits the transistor’s leakage current to generate a low frequency wake-up signal. This topology is compatible with IC technologies where only n-type transistors are available. The design was implemented with the sustainable FlexIC process of PragmatIC, that is based on Indium Gallium Zinc Oxide (IGZO) thin-film transistors. Our timer generates mean wake-up frequency of 0.24 ± 0.15 Hz, with a mean power consumption of 26.7 ± 14.1 nW. In this paper, we provide details of the Wake-Up timer’s design and performance at different supply voltages, under temperature variations and different light conditions.

Sn-based perovskite solar cells (PSCs) have attracted attention because of their low environmental impact. Unfortunately, the readily occurring oxidation of Sn²⁺ inhibits further improvement of their efficiency and stability. Ruddlesden–Popper (RP) Sn-based perovskites are considered promising candidates as absorbers that improve the performance and stability of Sn-based PSCs. However, microscopic understanding of performance-enhancing mechanisms remains insufficient. For this study, electron spin resonance (ESR) spectroscopy measurements were taken of RP Sn-based PSCs with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole-transport layers and (BA_0.5PEA_0.5)₂FA₃Sn₄I₁₃ perovskite layers to clarify the space-charge region formation mechanism at the PEDOT:PSS/(BA_0.5PEA_0.5)₂FA₃Sn₄I₁₃ interface. These results indicated electron-barrier formation in the (BA_0.5PEA_0.5)₂FA₃Sn₄I₁₃ layer near the PEDOT:PSS layer. Moreover, the electron barrier was found to be enhanced during device operation. The enhanced interface band bending reduces interface recombination and thereby improves the device's performance. These findings might provide important progress in practical applications of PSCs and might advance the realization of a carbon-neutral society.

Understanding the bending behaviour of a crystal onto a flexible platform is crucial for flexible electronics. The Young’s modulus, a measure of how easily a material deforms, plays a critical role in the coupled deformation of a crystal on a flexible substrate, as well as the transfer of strain from the substrate onto the layer. Here, we report on the bending behaviour of gallium selenide (GaSe), a van der Waals semiconductor with a small Young’s modulus and strain-dependent electronic band structure. A controllable, reproducible uniaxial strain, ϵ, is applied to nanometer-thick GaSe layers via their bending on a mica substrate. The spectral shift ΔE of the room temperature photoluminescence emission corresponds to a strain coefficient ΔE/ϵ of up to ~100 eV, the largest value reported in the literature to date. This is accompanied by coupled electronic and vibrational states under strain-induced resonant excitation conditions, as probed by Raman spectroscopy.