HEC/PEDOT: PSS-enhanced multi-crosslinked hydrogels for underwater motion sensors

A multi-cross-linked conductive hydrogel (ANHP) with HEC/PEDOT:PSS enhancement is designed for underwater motion sensing. • The ANHP hydrogel exhibits ultra-low equilibrium swelling ratio, outstanding tensile properties and high toughness. • The ANHP hydrogel sensor has high sensitivity, wide strain response range, fast response time and excellent cyclic stability. • The ANHP hydrogel detects multi-joint motions in air and underwater, and provides emergency signal sending via Morse code. Flexible conductive hydrogels, as core candidate materials for next-generation wearable sensors and underwater detection devices, show great potential for applications in Marine engineering, biomedical monitoring, and other fields. However, traditional conductive hydrogels tend to excessive swelling in the water environment due to abundant hydrophilic groups in their network structure, resulting in mechanical degradation and distortion of sensing signals, which seriously restricts their practical application in underwater scenarios. In this study, acrylamide (AM) and N-hydroxymethylacrylamide (NMA) were used as copolymerization monomers, hydroxyethyl cellulose (HEC) as the core biobased skeleton and multifunctional regulatory medium, and PEDOT:PSS as the high-conductivity functional filler to successfully construct a hydrogel (ANHP) with a multiple cross-linked structure. The test results show that the prepared hydrogel exhibits an extremely low equilibrium swelling ratio (3%), excellent tensile properties (0.614 MPa, 1343.81%), high sensitivity (GF = 3.35), a wide strain response range (0–400%), a fast response time (0.25 s), and outstanding cyclic stability over 500 cycles. The hydrogel-based sensor can stably detect human motions underwater and realize underwater Morse code communication. This study provides an innovative strategy for the development of high-performance underwater flexible sensors and an important reference for the high-performance and multifunctional application of carbohydrate-based functional materials. Download: Download high-res image (205KB) Download: Download full-size image Synthetic route and structural diagram of ANHP hydrogel.