Mixed-dimensional MXene-hydrogel heterostructures for electronic skin sensors with ultrabroad working range

Skin-mountable microelectronics are garnering substantial interest for various promising applications including human-machine interfaces, biointegrated devices, and personalized medicine. However, it remains a critical challenge to develop e-skins to mimic the human somatosensory system in full working range. Here, we present a multifunctional e-skin system with a heterostructured configuration that couples vinyl-hybrid-silica nanoparticle (VSNP)–modified polyacrylamide (PAM) hydrogel with two-dimensional (2D) MXene through nano-bridging layers of polypyrrole nanowires (PpyNWs) at the interfaces, featuring high toughness and low hysteresis, in tandem with controlled crack generation and distribution. The multidimensional configurations endow the e-skin with an extraordinary working range (2800%), ultrafast responsiveness (90 ms) and resilience (240 ms), good linearity (800%), tunable sensing mechanisms, and excellent reproducibility. In parallel, this e-skin platform is capable of detecting, quantifying, and remotely monitoring stretching motions in multiple dimensions, tactile pressure, proximity sensing, and variations in temperature and light, establishing a promising platform for next-generation smart flexible electronics.

Polypyrrole and polypyrrole@MnO2 nanowires grown on graphene foam for asymmetric supercapacitor

The asymmetric supercapacitor with negative electrode by graphene foam loaded Polypyrrole nanowires (PPy NWs/rGOF) and positive electrode by PPy@MnO2 core–shell nanowires on graphene foam (PPy@MnO2 NWs/rGOF) was developed. The negative electrode was further converted into the positive electrode by one-step redox reaction at room temperature. Graphene foam (rGOF) with unique flexibility, large surface area and high electric conductivity can favor in situ growth of polypyrrole nanowires (PPy NWs) as well as improve cycling stability of the resultant negative electrode. PPy NWs served as the ideal template for the formation of MnO2 shell gives rise to the as-prepared positive electrode with fast electron transport and enhanced active material utilization. Owing to the rational design, the assembled asymmetric supercapacitor was able to be repeatedly discharged/charged at 1.6 V, displaying high energy density of 1.04 mWh cm–3 with improved cycling stability.