Conformal, Substrate-Free Liquid Metal Electrode for Continuous Health Monitoring

Thin, skin-conformal soft electronics are ideal for seamless integration with the skin, enabling high-fidelity health monitoring and advanced human-machine interactions. However, achieving imperceptible and seamless adhesion with traditional materials and design approaches remains challenging as it is difficult to simultaneously meet the requirements of gas permeability, high conductivity, and conformability. In this work, we present a straightforward and efficient design for ultrathin, substrate-free, highly gas-permeable, and conductive liquid metal electrodes. These electrodes can be directly laminated onto human skin using water mist dissolution, facilitated by electrospun nanomeshes made from a poly(vinyl alcohol) and sodium dodecyl sulfate substrate. The electrodes have a thickness of 8.3 μm, a conductivity of 4.2 × 10⁶ S m^-1, and a gas permeability of 1283.8 ± 27.7 g m^-2 day^-1. A 24 h skin patch test demonstrated that the epidermal electrodes did not cause any skin irritation. Additionally, the electrodes exhibit excellent customizable patterning capabilities and recyclability. The electrodes successfully measure high-fidelity electrophysiological signals wirelessly, even during various daily activities such as sleep, work on the computer, and walking.