High mechanical strength, strong adhesion, self-healing and conductive ionic hydrogels for motion detection

Abstract

The development of conductive hydrogels with outstanding mechanical properties, robust adhesion, and high sensitivity is still a major challenge. This study successfully addresses this issue by a multi-functional ionic conductive hydrogel based on a highly entangled double network (DN) structure with excellent mechanical properties, strong adhesion, high sensitivity and self-healing ability. Polyacrylic acid (PAAc)/chitosan (CS) constructed the Double Network with physical entanglement as the main effective crosslinking. The sliding entanglement points made the hydrogel show a more uniform directional network structure during stretching, and the energy dissipation was greatly reduced. Active chemically reactive polydopamine (PDA), CS, and PAAc are complexed with aluminum ions (Al3+) respectively (building appropriate chemical crosslinking networks), and Al3+ acts as a “bridge” to build a hierarchical porous networks through multiple reversible coordination bond mediated interactions, alternating rigid and elastic domains, thereby improving the comprehensive performance of hydrogels. The tensile strength of PAAc/PDA/CS (ADC) was 173.4 kPa and the elongation at break was 921.9%, both of which were improved simultaneously. Moreover, ADC composite hydrogels exhibit excellent self-healing and adhesion properties, which can be attributed to the rich reversible/irreversible interactions brought about by PDA, with an impressive adhesion strength of 85.2 kPa on pig skin, further enhancing its practicality. Additionally, the ionic hydrogel demonstrates high strain sensitivity to tension, making it an ideal material for stable sensor signal output. The sensitivity coefficient (GF) reaches an impressive 11.24, highlighting the importance of this hydrogel in ensuring consistent and precise data collection. This innovative approach expands the idea and provides data support for the molecular structure design of high-performance wearable hydrogel sensors.