Highly Conductive and Stretchable Hydrogel Nanocomposite Using Whiskered Gold Nanosheets for Soft Bioelectronics

Abstract

The low electrical conductivity of conductive hydrogels limits their applications as soft conductors in bioelectronics. This low conductivity originates from the high water content of hydrogels, which impedes facile carrier transport between conductive fillers. This study presents a highly conductive and stretchable hydrogel nanocomposite comprising whiskered gold nanosheets. A dry network of whiskered gold nanosheets is fabricated and then incorporated into the wet hydrogel matrices. The whiskered gold nanosheets preserve their tight interconnection in hydrogels despite the high water content, providing a high-quality percolation network even under stretched states. Regardless of the type of hydrogel matrix, the gold-hydrogel nanocomposites exhibit a conductivity of approximate to 520 S cm-1 and a stretchability of approximate to 300% without requiring a dehydration process. The conductivity reaches a maximum of approximate to 3304 S cm-1 when the density of the dry gold network is controlled. A gold-adhesive hydrogel nanocomposite, which can achieve conformal adhesion to moving organ surfaces, is fabricated for bioelectronics demonstrations. The adhesive hydrogel electrode outperforms elastomer-based electrodes in in vivo epicardial electrogram recording, epicardial pacing, and sciatic nerve stimulation. High electrical conductivity (approximate to 520 S cm-1) and high stretchability (approximate to 300%) are achieved simultaneously for conductive hydrogel nanocomposite, through a sequential formation method using whiskered gold nanosheets. The maximum conductivity reaches 3304 S cm-1. The conductive hydrogel nanocomposite functionalized with tissue adhesive property realizes robust integration with living organs, demonstrating high-performance bioelectronics in vivo. image