Antibacterial zwitterionic hydrogel for flexible and wearable ultrafast-response strain sensors with low hysteresis

Zwitterionic hydrogels, with their unique antibacterial and tissue-adhesive nature, show great potential in the fields of wearable sensors, healthcare monitoring, and e-skins. However, it remains a huge challenge to integrate high elasticity and low hysteresis in such a hydrogel via simple methods. Herein, a novel tissue-adhesive zwitterionic hydrogel sensor was fabricated by a simple one-pot method using copolymerization of [2-(Methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA), N-[Tris (hydroxymethyl)methyl] acrylamide (THMA), and acrylic acid (AA), which was crosslinked by polyethylene glycol diglycidyl ether (PEGDE), a crosslinker famous for its low-toxicity and biocompatibility. The obtained SAT hydrogel shows robust elasticity with low hysteresis and fatigue resistance, which is essential for the long-term use. The introduction of THMA and PAA enhances the adhesive strength and reversible resilience of the hydrogel by interfacial hydrogen bonding, resulting in superior adhesion to skin without causing harm. The chemical crosslinker existing in SAT hydrogel enables it to withstand large deformations while maintaining stability. Besides the well-known antibacterial properties, the addition of SBMA enables the hydrogel to exhibit excellent electrical properties and a rapid response (19.5 ms) within a wide strain-sensing range, which facilitates accurate detection of various human body motions, such as joint bending, swallowing, and heartbeats. Moreover, the hydrogel demonstrates biocompatibility and excellent antibacterial activity, promising a safer and more comfortable experience for users.