Preparation of Conductive Hydrogels by Using the Triple Helix Structure of Gels

In this study, without introducing any chemical cross-linking agent, a high-strength and stretchable gelatin-based conductive hydrogel was prepared by simple and efficient physical blending using the unique triple-helical cross-linking structure of gel and the hydrogel physical cross-linking network formed by the hydrogen bonding between MFC and gel molecules. Fourier-transform infrared (FT-IR) was carried out to investigate interactions between MFC and gel, demonstrating that the hydrogel dimensional stability is mainly due to a mass of hydrogen bonds, which is formed by the polar groups (−OH) in MFC molecules and the polar groups (−OH, −NH2, and −C═O) in Gel molecules. The MFC, interestingly, can help to improve the dispersion of GR inside the hydrogel, which facilitates the formation of electron-conducting channels and facilitates electron transport, thereby increasing the electrical conductivity of the material; when the content of MFC is 6%, the conductivity of the hydrogel reaches the maximum value of 7.25 × 10–3 S/m. The strain sensor developed based on the GR/MFC/Gel hydrogel has excellent sensitivity (GF = 2.77), outstanding response ability (response time is 0.2 s, and recovery time is 0.3 s), and excellent cycle stability and can be used as a smart wearable material for real-time monitoring of human motions such as finger, elbow, and wrist bending, as well as tiny facial expressions such as smiling, opening mouth, frowning, and blinking. In addition, it can be used as an electronic pen to recognize complex handwriting and convert mechanical signals of the human body into real-time electrical signals.