Silk fibroin‐based conductive and antibacterial hydrogels with a dual network for flexible sensors

Abstract

The flexible wearable hydrogel strain sensors for human motion monitoring have attracted broad attention. However, developing a high‐strength hydrogel strain sensor remains challenging and achieves synergistic characteristics such as biocompatibility, antibacterial activity, and conductivity. This work proposes a two‐step UV polymerization method for the preparation of (hydrolyzed silk fibroin (HSF)/polyacrylamide (PAM)/polyacrylic acid (PAA)/poly sulfobetaine methacrylate (PSBMA) composite hydrogels. The monomers AM and AA undergo self‐polymerization and copolymerization. Meanwhile, SF is cross‐linked with them via multiple hydrogen bonds to form the first network. After the second UV initiation, SBMA polymerizes to create the second network. The HSF8%/PAM/PAA/PSBMA2% possesses superior tensile strength (1.49 ± 0.07 MPa) and compressive modulus (21.47 ± 1.07 MPa at 99% strain). The SBMA (4 wt%) endows hydrogels with antibacterial activity (98.53% ± 4.93%). The H+ ionized by PAA and the ion channels constructed by SBMA (4 wt%) provide hydrogel with ionic conductivity (0.950 S m−1). The hydrogel could be used as a flexible strain sensor to monitor human joint activity. The natural silk fibroin allows the hydrogel to retain degradability. Therefore, the SF‐based conductive hydrogel shows the potential application in flexible strain sensors.

Versatile Agar‐Zwitterion Hybrid Hydrogels for Temperature Self‐Sensing and Electro‐Responsive Actuation

“…For SBMA and PSBMA, the decrease of the stretching vibrations of C═C at 1639 cm −1 indicated the polymerization of the SBMA monomers. [17] Agar/PSBMA hybrid hydrogels displayed both stretching vibration absorption peaks of ─OH at 3436 cm −1 for Agar [18] and the characteristic peaks of S═O at 1032 and 1166 cm −1 , as well as C═O absorption peaks at 1717 cm −1 of PSBMA, [19] indicating that the double network of Agar physical cross-linking and PABMA chemical cross-linking was formed in the hydrogel. In addition, the absorption peak of O─H in Agar moved to higher wavenumbers and the absorption peak of S═O moved to lower wavenumbers, indicating the smaller strength of hydrogen bonding resulted from the interaction between Agar and PSBMA and the decreased physical cross-linking.…”