Synthesis of zwitterionic hydrogels by hydrophobic interaction and application of flexible sensors

Abstract

Flexible strain sensors need to obtain a stable signal as the target undergoes random and repeated deformation. Therefore, excellent mechanical properties, adhesion properties, and electrical conductivity are essential. In this study, a stretchable, self-adhesive, and conductive ionic hydrogel was designed and synthesized. Zwitterionic hydrogels were synthesized by micellar copolymerization of hydrophobic monomer methacrylate stearic acid (C18) with hydrophilic monomers [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA) in the presence of sodium dodecyl sulfate (SDS) surfactant. Compared with traditional chemical cross-linked hydrogels, the elongation at break is increased by 934%. The multi-walled carbon nanotubes (MWCNTs) modified with tannic acid (TA) have good dispersibility and stability, which can be added to the hydrogel as a functional filler to enhance the tensile and conductive properties of the sensor. The hydrogel flexible sensor prepared under the synergistic action of various mechanisms has good mechanical properties, bonding properties, and conductive properties. In addition, due to the inherent antibacterial properties of the raw material, the hydrogel has a bactericidal ratio of up to 99% against E. coli and S. aureus under the premise of good biocompatibility in vitro, which has great potential in the field of monitoring human movement and healthcare.

Graphical abstract