High-strength and highly electrically conductive hydrogels for wearable strain sensor

Highlights: • The chain-entangled chitosan network makes PAA/GO-Fe³⁺/CS DN hydrogels have high tensile strength (2.7 MPa). • The Na⁺ and Cl⁻ were introduced into the PAA/GO-Fe³⁺/CS DN hydrogel by immersion and the free Fe³⁺ of the hydrogel itself give the hydrogel high conductivity (13.8 S m⁻¹). Conductive hydrogels, important substrates for the manufacture of flexible electronic devices, are often used as components of wearable sensors, soft robots, and health monitoring equipment, due to their excellent conductivity, flexibility, and ease of processing. However, the requirements for the practical application of conductive hydrogels are difficult to satisfy, because a certain balance must be struck between their high mechanical properties and electrical conductivity. A self-healing dual network (DN) ion conductive hydrogel having a high tensile strength (2.7 MPa) and conductivity (13.8 S m⁻¹) was designed through a simple soaking strategy: polyacrylic acid/graphene oxide-ferric cation/chitosan (PAA/GO-Fe³⁺/CS). This hydrogel exhibits both high sensitivity in a wide linear range and long-term electrical stability. Based on these characteristics, a stretchable strain sensor was elaborated and successfully used in human motion monitoring. The PAA/GO-Fe³⁺/CS hydrogel shows a broad application prospect in the manufacture of flexible electronic devices.