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 −CO)
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.