Dual physical cross-linking supramolecular hydrogel with self-healing, recyclable and stretchable capabilities as wearable strain sensor for human motion monitoring

Hydrogel-based wearable sensors have attracted tremendous attention in the sensing electronics field due to their unique properties. However, it remains a challenge to explore hydrogel-based sensor that can incorporate highly stretchable, self-healing, and recyclable properties simultaneously. In this work, we report a simple approach to fabricate high-performance polymer hydrogels using (3-acrylamidopropyl) trimethylammonium chloride (ATAC), tannic acid (TA) and ferric chloride (FeCl₃) as raw materials. There were two non-covalent interactions in the network: hydrogen bonding between PATAC and TA, and metal-coordination interaction between TA and FeCl₃. Excellent mechanical properties were achieved of the PATAC-TA/Fe³⁺ hydrogel: fracture strain of 2234 %, fracture stress of 188.57 kPa, and toughness of 2.93 MJ/m³. Due to reversibility of the non-covalent cross-linked networks, the self-healing efficiency of the hydrogel could reach 96.62 % after 24 h of contact. At the same time, the stretchability, electrical conductivity, and self-healing property of the damaged hydrogel were recovered after dissolution and drying. Therefore, the strain sensor based on the hydrogel could be used to monitor a variety of human activities in real time, including speech recognition, facial expression recognition and joint bending. With the combination of these outstanding features, such a highly self-healing and recyclable hydrogel through a facile and green preparation process would have great potential application for sustainable wearable sensors.