Wearable Flexible Strain Sensors Based on Sodium Alginate–Polyacrylic Acid Double-Network Conductive Hydrogels

There are significant advantages in the field of wearable sensors offered by electronically conductive hydrogels, which exhibit exceptional mechanical properties, skin-like elasticity, and high electrical conductivity. In this study, a flexible sensor based on a conductive hydrogel with a double-network (DN) structure was prepared. Graphene and carboxyl-functionalized multiwalled carbon nanotubes (C-MWCNTs) were composited and integrated into a double-network hydrogel composed of sodium alginate (SA) and polyacrylic acid (PAA) to establish a conductive network framework. The results of the electromechanical response tests show that the prepared flexible sensor can make a stable and sensitive response to strain and pressure (a gauge factor (GF) of 6.46 and a pressure sensitivity of 0.034 kPa<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula>) and at the same time has good tensile properties (1023.71%), high tensile strength (303.62 kPa), and toughness (1.433 MJ/m3). Besides, the additional adhesion can provide convenient fixation requirements. The flexible sensors can not only monitor subtle human body movements but also detect the writing process of different words, which can effectively promote the application and development of flexible sensors in the fields of electronic wearable products and intelligent identification.