Tissue-Like Skin-Device Interface for Wearable Bioelectronics by Using Ultrasoft, Mass-Permeable and Low-Impedance Hydrogels

Hydrogels are composed of a cross-linked porous polymer structure with water molecules distributed within the gaps of the polymer chains. This unique composition renders hydrogels soft and hydrated, sharing mechanical and physical characteristics akin to human tissues. Consequently, hydrogels have the potential to emulate a tissue-like environment within the minuscule spaces between wearable devices and the human skin. In this study, we introduce strategies at both material and device levels to establish a quasi-solid, tissue-mimicking interface between wearable bioelectronics and human skin. A crucial element of this approach involves an ultra-thin functionalized hydrogel exhibiting exceptional properties like high mass-permeability and low impedance. This specialized hydrogel acts as a liquid electrolyte on the skin, creating a highly conformal and low-impedance interface suitable for wearable electrochemical biosensors and electrical stimulators. Moreover, its porous structure and ultra-thin profile enable efficient transport of target molecules across the interface, thereby maximizing the performance of diverse wearable bioelectronics.