A highly tough, fatigue-resistant, low hysteresis hybrid hydrogel with a hierarchical cross-linked structure for wearable strain sensors

Abstract

Hydrogels are considered to be one of the promising candidates for wearable sensors due to their ideal designability and excellent mechanical flexibility. Nevertheless, the preparation of ion-conductive hydrogels with excellent mechanical properties by simple methods remains a great challenge. Herein, a unique hierarchical cross-linked network is fabricated in a polyacrylamide–hyaluronic acid (PAM–HA) hybrid hydrogel, achieving a dramatic improvement in the overall mechanical properties of the system. This hydrogel has been shown to have ideal transmittance (>90%), super stretchability (with a breaking elongation of 3040%), high mechanical strength (breaking strength up to 317.8 kPa), satisfactory toughness (3.07 MJ m⁻³), and excellent fatigue resistance. Furthermore, the hybrid hydrogel also shows remarkable self-adhesive performance on different substrates, including ceramics, glass, metals, plastics, and pigskin, and maintains a stable repeat adhesion strength. Attractively, the hydrogel-based strain sensor shows an amazing detection range of over 1000% and a lower detection limit of 1%, which enables it to accurately capture and monitor large and subtle human motions. This work can provide a new method for the construction of hydrogels with ideal comprehensive mechanical properties and promote the application of hydrogels in the field of wearable sensors.