Highly tough supramolecular double network hydrogel electrolytes for an artificial flexible and low-temperature tolerant sensor

Abstract

High-performance hydrogel electrolytes with eminent toughness, high conductivity and anti-freezing properties have extensive applications in wearable devices or implantable sensors. However, it is still difficult to integrate excellent mechanical properties and high conductivity into one hydrogel sample simultaneously. This work introduced NaCl into a poly(vinyl alcohol)/poly(acrylic amide) (PVA/PAM) double network hydrogel to prepare PVA/PAM/NaCl supramolecular hydrogel electrolytes via a one-pot method. NaCl introduces physical entanglement into the PVA/PAM/NaCl hydrogel electrolytes and provides a dense and wrinkled three dimensional (3D) network nanostructure. The PVA/PAM/NaCl hydrogel electrolytes not only showed excellent mechanical properties (tensile strength up to 477 kPa, elongation at break to 1072% and a fracture energy of 2.484 MJ m⁻³), but also had high conductivity (up to 6.23 S m⁻¹). A strain sensor based on the PVA/PAM/NaCl hydrogel electrolytes exhibited very high sensitivity (gauge factor = 24.901) with the ability of precise and reliable detection of human motions. Hydrogels also showed excellent anti-freezing properties and maintained excellent mechanical properties and conductivity at −20 °C. Introducing a physically cross-linking network through the effects of a metal salt could promote the performance of the hydrogels. This work provides a new insight into the design of multifunctional materials with applications on electronic skin, wearable devices and biosensors.