Hydrogels are promising materials for electronic skin due to their flexibility and modifiability. Reported hydrogel electronic skins can recognize stimulations and output signals, but the single output signal and the requirement of external power source limit their further applications. In this study, inspired by the neuron system, the self-powered neuron system-like hydrogels based on gelatin, water/glycerin and ionic liquid modified metal organic frameworks (MOFs) are prepared. The optimized hydrogel exhibits excellent adhesion (40 kPa), stretchability (0%-100%), water retention (>92% at 0% relative humidity (RH) atmosphere), ionic conductivity (>10 −3 S m −1 ) and stability (>30 days). Besides, the neuron system-like hydrogels are highly sensitive to pressure (0-10 N) and humidity (0%-75% RH) with dual-modal output, without external power source. Finally, the optimized hydrogel ionic skin is applied in human motion detection, energy harvesting, and low humidity sensing. This study provides a preliminary exploration of self-powered ionic skin for multi-application scenarios.
In this paper, strong hydrophilic poly(ionic liquid)s (PILs) are selectively grafted on different positions (mesoporous channels and outer surface) of mesoporous silica via thiol‐ene click chemical reaction. The purposes of selective grafting are on the one hand, to explore the differences of adsorption and transportation of water molecules in mesoporous channels and on the outer surface, and on the other hand, to combine the two approaches (intra‐pore grafting and external surface grafting) to reasonably design SiO2@PILs low humidity sensing film with synergetic function to achieve high sensitivity. The results of low relativehumidity (RH) sensing test show that the sensing performance of humidity sensor based on mesoporous silica grafted with PILs in the channels is better than that of humidity sensor based on mesoporous silica grafted with PILs on the outer surface. Compared with water molecules transport single channel, the construction of dual‐channel water transport significantly improves the sensitivity of the low humidity sensor, and the response of the sensor is up to 4112% in the range of 7–33% RH. Moreover, the existence of micropores and the formation of dual‐channel water transport affect the adsorption/desorption behaviors of the sensor under different humidity ranges, especially below 11% RH.
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