Functional Structural Color Hydrogel Adhesives for Soft Robotic Epidermal Sensing

Structural color hydrogels are promising material candidates for optical displays, smart sensing, and biological interfaces. However, it is still a challenge to formulate structure color hydrogels with multifunctionality (e.g. robust toughness, strong adhesion, high stretchability, and high electronic conductivity) without compromising their intrinsic optical properties. In this paper, we report a multifunctional structural color hydrogel by incorporating a conductive polymer Poly(3,4-ethylenedioxythiophene)-poly (styrene sulfonate) (PEDOT: PSS) into a mechanically robust poly (vinyl alcohol) (PVA)/poly (acrylic acid) (PAA) double network (DN) hydrogel. The as-prepared structural color hydrogel could span a wide range of mechanical properties by simply tuning the polymer composition and the number of freezing-thawing cycles. The dynamic hydrogen bonding interactions endow the hydrogel sensor with reversible adhesion to different substrates. In particular, the structural color hydrogel shows high sensitivity in optical and electronic sensing capability, and can accurately detect some human movements. This work provides useful insights into the development of functional structural colors for wearable soft electronics.