An adhesive, low swelling and conductive tri-network hydrogel for wearable electronic devices

Abstract

Conductive hydrogels have great potential in wearable electronic devices for motion detection and medical monitoring applications. However, poor tissue adhesion and underwater swelling remain challenging for most hydrogels as in vitro wearable electronic devices. Herein, a tri-network (TN) hydrogel consisting of agarose (AG), amphoteric sulfobetaine methacrylate (SBMA) and polypyrrole (PPy) is developed to solve these problems. Owing to the ionic dipole interactions and cation–π interactions of SBMA, the novel developed hydrogel exhibits good adhesion capability. AG and PPy improve the cross-linking density of the hydrogels, thus improving their resistance to swelling underwater. In addition, the TN hydrogel has less substrate noise interference and high strain sensitivity, which enables it to monitor electrical signals generated by subtle motion variation. Due to the cross-linking of double helical bundles formed by hydrogen bonding in AG linear molecules, the dipole-ionic interactions between sulfonic acid groups and quaternary ammonium cations in SBMA, and the conjugated π-system constituted by alternating single and double bonds in Ppy, the TN hydrogel exhibits good mechanical and electrical conductivity properties. Therefore, this study provides a strategy to generate stretchable, compressive, and conductive hydrogels with adhesive properties and can be used in underwater environments, expanding the potential applications of hydrogels as wearable electronic devices.