Developing a cotton fabric sensing layer with good waterproofness and breathability via a low-cost and eco-friendly method is increasingly important for the construction of comfortable and wearable electronic devices. Herein, a waterproof and breathable cotton fabric composite decorated by reduced graphene oxide (rGO) and carbon nanotube (CNT), Cotton/rGO/CNT, is reported by a facile solution infiltration method, and we adopt such Cotton/rGO/CNT composite to develop a layer-by-layer structured multifunctional flexible sensor, enabling the high-sensitivity detection of pressure and temperature stimulus. Particularly, the multifunctional flexible sensor exhibits a high response toward tiny pressure, demonstrating salient superiority in the continuous and reliable monitoring of human physiological information. Concerning temperature sensing, a good linear response for the temperatures ranging from 28 to 40 °C is achieved by the multifunctional flexible sensor and gives rise to be successfully applied to the non-contact real-time monitoring of human respiration signal. Finally, an array consisting of multifunctional flexible sensors further demonstrates its feasibility in perceiving and mapping the pressure and temperature information of contact objects. This work provides a feasible strategy for designing cotton-based sensing layers that can effectively resist liquid water penetration and allow water vapor transmission, and offers reasonable insight for constructing comfort and multifunctional wearable electronics.

Environmentally friendly biomimetic materials with good deformability, high pressure-sensitive performance, and excellent biocompatibility are highly attractive for health monitoring, but to simultaneously meet these requirements is a formidable challenge. In this study, biocompatible MXene quantum dot (MQD)/watermelon peel (WMP) aerogels were obtained by immersing freeze-dried fresh watermelon peel into the quantum dot dispersion. The resulting bio-aerogels with a three-dimensional (3D) porous network structure exhibited a low in elasticity modulus (0.03 MPa) and limit of detection (0.4 Pa) and it showed biocompatibility. With a maximum pressure-sensitive response of 323 kPa^－1, the 3D porous MQD/WMP aerogels exhibited good stability. In addition, the sensing signals could be displayed on mobile phones through a Bluetooth module to monitor human motion (pulse, sound, and walking) in real time. More importantly, the MQD/WMP aerogels exhibited excellent biocompatibility in a cytotoxicity test, thus decreasing the safety risk when they are applied to human skin. The finding in this study will facilitate the fabrication of high-performance biomimetic MXene active matrices, which are derived from natural biological materials, for flexible electronics.

High-performance energy storage and sensing devices have been undergoing rapid development to meet the demand for portable and wearable electronic products, which require flexibility, extensibility, small volume and lightweight. In this study, we construct a lightweight and flexible self-powered sensing system by integrating a highly stretchable strain sensor with a high-performance asymmetric supercapacitor based on ZnSe/CoSe₂//ECNT (ECNT: electrochemically activated carbon nanotube film). The ZnSe/CoSe₂ two-dimentional nanosheets on carbon nanotube (CNT) films are synthesized through a simple and efficient strategy derived from ZnCo-based metal-organic frameworks (MOFs). The density functional theory (DFT) simulations show the higher conductivity of the ZnSe/CoSe₂/CNT electrode than the CoSe₂/CNT electrode. Due to the synergistic properties of self-supported two-dimentional ZnSe/CoSe₂ nanosheets with high specific surface area and the high pathway of one-dimention CNTs, the nanocomposite electrode provides efficient transmission and short paths for electron/ion diffusion. The asymmetric supercapacitor provides a stable output power supply to the sensors that can precisely respond to strain and pressure changes. The sensor can also be attached to a garment for measuring a variety of joint movements.

Cd₃As₂ nanowires (NWs) have great potential in the near-infrared (NIR) photodetection field due to their excellent optoelectronic properties as a typical Dirac semimetal. However, the existence of surface oxidization limits their photoresponse performance for practical applications. Here, we modified the surface of Cd₃As₂ NWs with sulfur to prevent surface oxidizing and optimize the bandgap structure to improve the photoresponse performance. The S-modified Cd₃As₂ samples existed as core/shell Cd₃As₂/CdS NWs and the corresponding single NW device showed a responsivity of 0.95 A/W in the NIR band at a 0 V bias, which is three orders of magnitude higher than that of an unmodified NW. This study provides an efficient and universally applicable way to prevent semimetals nanostructures from oxidizing and promote their optoelectronic properties.

The weft-knitted reduced graphene oxide (r-GO) textile that is made up of many conductive r-GO coated fibers was successfully prepared dependent on the electrospray deposition technique. Interestingly, the r-GO textile presents negative resistance variation not only in axial direction as the pressure increases but also in transverse direction as the lateral stretch increases which makes it has the advantage to fabricate the reliable sensors based on strain-resistance effect. The transverse-strain and pressure sensors based on the r-GO textiles all show the excellent sensing characteristics such as high sensitivity, reliability, and good durability, etc. The maximum gauge factors (GF) of the transverse-sensor are 27.1 and 153.5 in the x- and y-direction, respectively. And the practical detection range can up to 40% in the x-direction and 35% in the y-direction, respectively. The r-GO textile pressure sensor also shows high sensitivity for a broad pressure range that with a GF up to 716.8 kPa^-1 for less than 4.5 kPa region and still has more sensitive pressure sensing characteristics even the pressure goes up to 14 kPa. Based on those good performances of r-GO textile sensors, its potential applications in human body states monitoring have been studied.

Chemical sensors (CSs) are an emerging area in nanoscience research, which focuses on the highly sensitive detection of toxic and hazardous gases and disease-related volatile organics. While the field has advanced rapidly in recent years, it lacks the theoretical support required for the rational design of innovative materials with tunable measurement responses. Herein, we present a one-dimensional (1D) hybrid nanofiber decorated with ultrafine NiO nanoparticles (NiO NPs) as an efficient active component for CSs. Highly dispersed (110)-facet NiO NPs with a high percentage of Ni²⁺ active sites with unsaturated coordination were confined in a TiO₂ nanofiber (TiO₂ NF) matrix that is favorable for surface catalytic reactions. The CSs constructed using the 1D heterostructure NiO/TiO₂ nanofibers (NiO/TiO₂ HNFs) exhibited a highly selective response to trace CO gas molecules (1 ppm) with high sensitivity (ΔR/R₀ = 1.02), ultrafast response/recovery time (T_res/T_recov < 20 s), and remarkable reproducibility at room temperature. The density functional theory (DFT) simulations and experimental results confirmed that the selective response could be attributed to the high molecular adsorption energy of the NiO nanoparticles with (110) facets and abundant interfaces, which act synergistically to promote CO adsorption and facilitate charge transfer.

Ammonia (NH₃) detection at room temperature has attracted considerable attention because of the increasing demand for health monitoring, personal safety protection, and industrial manufacturing. Herein, we report the synthesis of polycrystalline SrGe₄O₉ nanotubes (NTs) via an electrospinning process. These NTs are a new sensing material for the detection of ammonia at room temperature. The SrGe₄O₉ NTs exhibited a maximum sensing response of 2.49 for 100 ppm NH₃, which was increased to 7.08 by decorating the NTs with Pt nanoparticles. Flexible gas sensors were fabricated, which exhibited comparable performance to the rigid device. Additionally, the flexible devices showed excellent flexibility, mechanical stability, and sensing stability under different bending states, manifesting their potential applications in flexible and wearable electronics.

Wearable gas sensors that are lightweight, portable, and inexpensive have great potential application in the real-time detection of human health and environmental monitoring. In this work, we fabricated flexible fiber gas sensors with single-walled carbon nanotube (SWCNT), multi-walled carbon nanotube (MWCNT), and ZnO quantum dot-decorated SWCNT (SWCNTs@ZnO) sensing elements. These flexible fiber gas sensors could be operated at room temperature to detect target gases with good sensitivity and recovery time. They also exhibited superior long-term stability, as well as good device mechanical bending ability and robustness. Integrating these flexible gas sensors into face masks, the fabricated wearable smart face masks could be used to selectively detect C₂H₅OH, HCHO, and NH₃ by reading the corresponding LEDs with different colors. Such face masks have great potential application in the Internet of Things and wearable electronics.

Micro-supercapacitors (MSCs) as important on-chip micropower sources have attracted considerable attention because of their unique and advantageous design for optimized maximum functionality within a minimized sized chip and excellent mechanical flexibility/stability in miniaturized portable electronic device applications. In this work, we report a novel, high-performance flexible integrated on-chip MSC based on hybrid nanostructures of reduced graphene oxide/Fe₂O₃ hollow nanospheres using a microelectronic photo-lithography technology combined with plasma etching technique. The unique structural design for on-chip MSCs enables high-performance enhancements compared with graphene-only devices, exhibiting high specific capacitances of 11.57 F·cm^-3 at a scan rate of 200 mV·s^-1 and excellent rate capability and robust cycling stability with capacitance retention of 92.08% after 32, 000 charge/discharge cycles. Moreover, the on-chip MSCs exhibit superior flexibility and outstanding stability even after repetition of charge/discharge cycles under different bending states. As-fabricated highly flexible on-chip MSCs can be easily integrated with CdS nanowire-based photodetectors to form a highly compacted photodetecting system, exhibiting comparable performance to devices driven by conventional external energy storage units.

On-chip microsupercapacitors (MSCs) compatible with on-chip geometries of integrated circuits can be used either as a separate power supply in microelectronic devices or as an energy storage or energy receptor accessory unit. In this work, we report the fabrication of flexible two-dimensional Ni(OH)₂ nanoplates-based MSCs, which achieved a specific capacitance of 8.80 F/cm³ at the scan rates of 100 mV/s, losing only 0.20% of its original value after 10, 000 charge/discharge cycles. Besides, the MSCs reached an energy density of 0.59 mWh/cm³ and a power density up to 1.80 W/cm³, which is comparable to traditional carbon-based devices. The flexible MSCs exhibited good electrochemical stability when subjected to bending at various conditions, illustrating the promising application as electrodes for wearable energy storage.