Neuron‐Inspired Self‐Powered Hydrogels with Excellent Adhesion, Recyclability and Dual‐Mode Output for Multifunctional Ionic Skin

Abstract

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.

Force-Induced Single-Ion Transport in Porous Polyelectrolyte Hydrogels for Dual-Mode Output Sensing

“…Self-Powered Sensing Performance Test. The basic theory of hydrogel self-powered sensing is the potential formed by the different migration rates of anions and cations in the hydrogel, 11,36 but the migration pattern of ions in hydrogels is not clear. The anionic electrolyte hydrogels we constructed allow for a better understanding of ion migration under dynamic driving.…”

“…Some researchers achieved higher energy conversion efficiency by constructing pore gradients, salt concentration gradients, , moisture gradients, and an ion diode. ,− The movement of ions in the hydrogel creates ionic gradients, which results in a streaming potential signal. The strength and duration of the signal depend on the difference in cation and anion migration rates. , The diffusion rate of anions is relatively slow due to their large size and enrichment at the strain position …”

Ionic Liquid-Functionalized Metal–Organic Frameworks/Covalent–Organic Frameworks for CO2 Capture and Conversion

“…Meanwhile, the MOFs/COFs could also serve as the support of ILs, and thus, the recycling issue could be addressed. Hence, the coordination of ILs and MOFs/COFs achieve the “win–win” goal in materials synthesis and advanced applications, such as gas separation, adsorption, sensing, lithium-ion batteries, ionic conduction, and skin. − …”

Selective Encapsulation of Ionic Liquids in UiO-66-NH2 Nanopores for Enhanced Humidity Sensing

“…Humidity sensors have received widespread attention because they can be applied for real-time humidity detection in warehouses, factories, etc. In recent years, the application of humidity sensors has been expanded to human breath detection, noncontact switches, low humidity sensing, etc.…”