Design and performance of an ultra-sensitive and super-stretchable hydrogel for artificial skin

Designing skin-comparable conductive hydrogels has attracted tremendous interests, while it remains challenging to simultaneously achieve super-extensibility and ultra-sensitivity. Herein, a novel hydrogel was successfully fabricated to tackle this problem by using acrylamide (AM), flowerlike micelle (polyethylene glycol dilaurate) and sodium chloride (NaCl) as the monomer, cross-linker and conductive filler, respectively. The synergy of micelle deformation under external loads and chain entanglement between polyethylene glycol and polyacrylamide chains endowed the gel with ultra-stretchable property (elongation at break of 155 mm/mm). Meanwhile, the dipole-dipole interactions between ions and polymeric chains led to the ultra-sensitive capacity (gauge factor = 54.5, tensile strain of 20~30 mm/mm), superior to most hydrogel-based sensors. Therefore, the obtained sensor could precisely monitor various human motions, including finger bending at different angles, speaking, walking and running. Additionally, the presence of ions (Na+, Cl-) endowed the gel with excellent anti-freezing property (128 mm/mm of tensile strain at -20 ℃). This work sheds light on the fabrication of high-performance sensors and will broaden their applications.