Fig. 4. Imperceptible, artifact-free skin-interfaced bioelectronics.

(A) Schematic illustration of a skin-interfaced bioelectronic system, comprising skin-mounted bioelectronic patches with porous composite electrodes patterned on porous PU, imperceptible interconnection cables of porous composites, and mobile data acquisition modules. (B) Photograph of a porous EGaIn composite cable under high stretching (~500%). Scale bar, 1 cm. (C) Schematic of the simplified structure for FEA simulations, together with skin anatomy. (D) Simulation results for the von Mises stress distribution when stretching the porous EGaIn composite cable (top, 46% strain) and the ACF cable (bottom, 0.2% strain). (E) Simulation results for stresses induced on the skin surface (red) and the bottom epidermis (80 μm in depth; black) as a function of strains applied to the porous EGaIn composite cable and the ACF cable. Imperceptible areas represent the strains at which induced stresses are less than 20 kPa (the perception limit of human skin). (F) Photographs of stretching the porous EGaIn composite cable (left) and the ACF cable (right). Here, the initial length and displacement of the porous composite cable and ACF cable are identical. (G) Questionnaire results of discomfort levels of 20 volunteers after wearing skin-interfaced bioelectronic systems (fig. S25) for 24 hours, which are interconnected with the porous EGaIn composite cable, ACF cable, and PVC-insulated copper wire. (H) Concurrent ECG and ICG recording using skin-interfaced bioelectronics based on porous EGaIn composites. a.u., arbitrary units. (I) Magnified ECG and ICG signals in (H). (J) SNR of ECG signals recorded with porous composite electrodes and Ag/AgCl electrodes when stretching, relaxing, and compressing the electrodes. (K) SNR of ECG signals recorded using porous EGaIn composite electrodes when stretching interconnection cables made of porous EGaIn composites, Ag flakes composites, and AgNWs composites. Error bars in (J) and (K) represent SDs of six samples.