Conventional epidermal bioelectronics usually do not conform well with natural skin surfaces and are susceptible to motion artifact interference, due to incompatible dimensions, insufficient adhesion, imperfect compliance, and usually require complex manufacturing and high costs. We propose in situ forming hydrogel electrodes or electronics (ISF-HEs) that can establish highly conformal interfaces on curved biological surfaces without auxiliary adhesions. The ISF-HEs also have favorable flexibility and soft compliance comparable to human skin (≈0.02 kPa-1), which can stably maintain synchronous movements with deformed skins. Thus, the as-prepared ISF-HEs can accurately monitor large and tiny human motions with short response time (≈180 ms), good biocompatibility, and excellent performance. The as-obtained nongapped hydrogel electrode-skin interfaces achieve ultralow interfacial impedance (≈50 KΩ), nearly an order of magnitude lower than commercial Ag|AgCl electrodes as well as other reported dry and wet electrodes, regardless of the intrinsic micro-obstacles (wrinkles, hair) and skin deformation interference. Therefore, the ISF-HEs can collect high-quality electrocardiography and surface electromyography (sEMG) signals, with high signal-to-noise ratio (SNR ≈ 32.04 dB), reduced signal crosstalk, and minimized motion artifact interference. Simultaneously monitoring human motions and sEMG signals have also been implemented for the general exercise status assessment, such as the shooting competition in the Olympics. The as-prepared ISF-HEs can be considered as supplements/substitutes of conventional electrodes in percutaneously noninvasive monitoring of multifunctional physiological signals for health and exercise status.
Keywords: electromyography recording; epidermal bioelectronics; highly conformal interface; in situ forming; motion monitoring.