3D printing conductive hydrogel with low modulus and anti‐swelling for customized strain sensors

Abstract Developing antiswelling hydrogel that retains their low modulus and has three‐dimensional (3D) printability to application in the biomedical field is a current critical issue. Here, we synthesized 3D printing ink consist of poly(acrylic acid‐acrylamide‐allyloxypolyethyleneglycol) (P(AA‐Am‐APEG)) and nanosilica (SiO 2 ) by free radical polymerization, immersed the hydrogel precursor printed by ink in ferric chloride solution to prepare a low modulus, antiswelling, and conductive hydrogel. In the physical cross‐linking network, the coordination interaction and hydrogen bonds contributed to excellent mechanical properties and nSiO 2 regulated rheological behavior of ink. Especially, P(AA‐Am‐APEG) molecular chain was a structure containing of APEG branch chain, which could endow antiswelling (the equilibrium swelling rate was only 7% in deionized water) and low modulus (Young's modulus was less than 100 kPa) to hydrogel. The tensile stress could still maintain 90% of the original value after soaking for 24 h. In addition, the existence of iron and chloride ions provided high sensitive deformation‐dependent conductivity to hydrogel. Therefore, the strategy of controlling the swelling and modulus by branch chains would expand the application of hydrogel in biosensors and other fields.