We present a useful ammonia gas sensor based on chemically reduced graphene oxide (rGO) sheets by self-assembly technique to create conductive networks between parallel Au electrodes. Negative graphene oxide (GO) sheets with large sizes (>10 μm) can be easily electrostatically attracted onto positive Au electrodes modified with cysteamine hydrochloride in aqueous solution. The assembled GO sheets on Au electrodes can be directly reduced into rGO sheets by hydrazine or pyrrole vapor and consequently provide the sensing devices based on self-assembled rGO sheets. Preliminary results, which have been presented on the detection of ammonia (NH₃) gas using this facile and scalable fabrication method for practical devices, suggest that pyrrole-vapor-reduced rGO exhibits much better (more than 2.7 times with the concentration of NH₃ at 50 ppm) response to NH₃ than that of rGO reduced from hydrazine vapor. Furthermore, this novel gas sensor based on rGO reduced from pyrrole shows excellent responsive repeatability to NH₃. Overall, the facile electrostatic self-assembly technique in aqueous solution facilitates device fabrication, the resultant self-assembled rGO-based sensing devices, with miniature, low-cost portable characteristics and outstanding sensing performances, which can ensure potential application in gas sensing fields.

The rapid development of Internet of Things mobile terminals has accelerated the market's demand for portable mobile power supplies and flexible wearable devices. Here, an embedded metal‐mesh transparent conductive electrode (TCE) is prepared on poly(ethylene terephthalate) (PET) using a novel selective electrodeposition process combined with inverted film‐processing methods. This embedded nickel (Ni)‐mesh flexible TCE shows excellent photoelectric performance (sheet resistance of ≈0.2–0.5 Ω sq⁻¹ at high transmittance of ≈85–87%) and mechanical durability. The PET/Ni‐mesh/polymer poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS PH1000) hybrid electrode is used as a transparent electrode for perovskite solar cells (PSCs), which exhibit excellent electric properties and remarkable environmental and mechanical stability. A power conversion efficiency of 17.3% is obtained, which is the highest efficiency for a PSC based on flexible transparent metal electrodes to date. For perovskite crystals that require harsh growth conditions, their mechanical stability and environmental stability on flexible transparent embedded metal substrates are studied and improved. The resulting flexible device retains 76% of the original efficiency after 2000 bending cycles. The results of this work provide a step improvement in flexible PSCs.

Flexible transparent electrodes (FTEs) with high stability and scalability are in high demand for the extremely widespread applications in flexible optoelectronic devices. Traditionally, thin films of indium thin oxide (ITO) served the role of FTEs, but film brittleness and scarcity of materials limit its further application. This review provides a summary of recent advances in emerging transparent electrodes and related flexible devices (e.g., touch panels, organic light-emitting diodes, sensors, supercapacitors, and solar cells). Mainly focusing on the FTEs based on carbon nanomaterials (e.g., carbon nanotubes and graphene) and metal materials (e.g., metal grid and metal nanowires), we discuss the fabrication techniques, the performance improvement, and the representative applications of these highly transparent and flexible electrodes. Finally, the challenges and prospects of flexible transparent electrodes will be summarized.

Conventional fabrication methods for realization of metal mesh (MM) based transparent conductive film (TCF) are not economic and environmentally friendly. By combination of the scrape and selective electroplating techniques, a vacuum sputtering/evaporation-free process is explored for fabrication of high-performance MM based TCF. The fabricated TCF exhibits ultra-low sheet electrical resistance (Rs = 0.07 Ω sq−1) at average transmittance of 83% in visible region. The sample cannot only exhibit high heating temperatures (140 °C) at low input voltage (1.5 V) with fast and stable thermal response but provide high electromagnetic interference shielding efficiency (EMI SE) more than 43 dB in X-band. The processing chain provides a robust, powerful and scalable platform, which may open up a new avenue for realizing multifunctional TCF in diverse applications.

Piezoresistive composite elastomers have shown great potentials for wearable and flexible electronic applications due to their high sensitivity, excellent frequency response, and easy signal detection. A composition membrane sensor with an interlocked structure has been developed and demonstrated outstanding pressure sensitivity, fast response time, and low temperature drift features. Compared with a flexible MXene-based flat sensor (Ti₃C₂), the interlocked sensor exhibits a significantly improved pressure sensitivity of two magnitudes higher (21.04 kPa⁻¹), a fast reaction speed of 31 ms, and an excellent cycle life of 5000 test runs. The viability of sensor in responding to various external stimuli with high deformation capacity has been confirmed by calculating the force distribution of a polydimethylsiloxane (PDMS) film model with a microlens structure using the solid mechanics module in COMSOL. Unlike conventional process, we utilized three-dimensional (3D) laser-direct writing lithography equipment to directly transform high-precision 3D data into a micro-nano structure morphology through variable exposure doses, which reduces the hot melting step. Moreover, the flexible pressure device is capable of detecting and distinguishing signals ranging from finger movements to human pulses, even for speech recognition. This simple, convenient, and large-format lithographic method offers new opportunities for developing novel human–computer interaction devices.