Thermogalvanic gel patch for self-powered human motion recognition enabled by photo-thermal-electric conversion

Quasi-solid-state electrolytes offer a cheap, leak-free, and scalable way to convert heat directly into electricity for wearable electronics. However, the limited temperature difference with the environment poses a challenge for the extensive application of thermoelectric gels. Currently, photo-thermal-electric (PTE) conversion is an environmentally-friendly technology to exploit the thermogalvanic effect of gels. Here, we report a smart light-driven flexible PTE gel for self-powered human motion monitoring. The whole structure takes advantage of the low thermal conductivity and high output power of poly(vinyl alcohol)/polydimethylsiloxane (PVA-PDMS) gels with Fe2+/3+ as a redox pair, together with the local surface plasmon resonance (LSPR) of Au nanoparticles (AuNPs)@SiO2-PDMS composite film. This enables simultaneous high thermogalvanic and photothermal performance, with an open circuit voltage of up to 12 mV and a short circuit current exceeding 1.25 A m−2 at a temperature difference of up to 9 °C under one sun. The PTE gel is fabricated into a proof-of-concept self-powered patch, which can actively distinguish human motions in real time by recognizing the switching of solar radiation stimulated by arm swing. This work provides thermogalvanic gels with a new opportunity in self-powered wearable sensing that may greatly promote the progress of intelligent medical electronics.