Multifunctional smart mask: Enabling self-dehumidification and self-powered wearables via transpiration-driven electrokinetic power generation from human breath

Self-operating transpiration-driven electrokinetic power generators (STEPGs) offer an attractive approach for autonomous electricity production, but they suffer from a narrow range of applications due to the need for a highly humid environment. Herein, we introduce an efficient STEPG and its unprecedented application in the design of a multifunctional smart mask with self-dehumidification capability and self-powered wearable sensors. Our STEPG design for the smart mask comprises of (1) a carbon black-loaded cotton fiber (CB/CF) serving as a hydrophilic, electroactive platform for power generation, and (2) a moisture-absorbing desiccant layer to wet and activate the power generator. As-optimized STEPG achieves efficient energy conversion with a high V_OC, I_SC, and power output up to 1200 mV, 5 μA, and 687 nW/cm², respectively, under 10 °C (simulating winter temperature) and 90 %RH. These electrical outputs are > 8-fold better than similar TEPG designs, and are also stable under a wide range of ambient temperature (e.g. 10–40 °C) and humidity (e.g. 30–90 %RH). As a proof-of-concept application, we incorporate as-designed STEPGs in series onto a N95 mask to harness electrical energy directly from human breath and use it to power inbuilt temperature/humidity sensors for real-time, wireless monitoring of breath using a smart phone. By showcasing the facile use of human breath as an energy feedstock, our work creates enormous opportunities for diverse applications in green energy production and wearable technologies.