Tara Tannin-Cross-Linked,\nUnderwater-Adhesive, Super\nSelf-Healing, and Recyclable Gelatin-Based Conductive Hydrogel as\na Strain Sensor

Abstract

Conductive hydrogel strain sensors have triggered extensive\nresearch\ninterest in artificial intelligence, human motion detection, electronic\nskin, and other technical fields. However, it is still challenging\nwork to prepare conductive hydrogels integrated with good biocompatibility,\nrecyclability, self-healing, and strong adhesion properties both in\nair and underwater. Herein, a novel, ultraexcellent self-healing,\nadhesive, and multifunctional gelatin composite hydrogel was fabricated\nthrough a simple and rapid one-pot method in which gelatin (Gel) and\npolyvinyl alcohol (PVA) were used as the polymeric skeletons, Tara\ntannin as the cross-linking agent, and multiwalled carbon nanotubes\n(CNTs) as the conducting medium. Inspired by the vegetable tanning\nmechanism in tanning chemistry, the multiple hydrogen bonding and\nhydrophobic interactions of Tara tannin with Gel were used to build\nthe cross-linking network of the hydrogel. The obtained GTPC (Gel-Tara\ntannin-PVA-CNTs) hydrogel exhibited considerable stretchability (760%),\nstrong adhesion strength (16 kPa to pigskin), and high conductive\nsensitivity (gauge factor (GF) = 6.79). In particular, the GTPC hydrogel\ndisplayed good repeatable adhesion (≥10 times) and rapid self-healing\nperformance (HE (self-healing efficiency) > 99%) both in air and\nunderwater.\nThe formed GTPC hydrogel strain sensor could accurately detect various\nmotion signals, such as finger bending, ankle bending, and smiling,\nand it could also sensitively capture sensing signals of body movements\nunderwater. The self-healed hydrogel sensor also exhibited a similar\nmotion sensing ability to the original one. This work affords a new\nidea and method for the design and fabrication of flexible strain\nsensors with rapid air and underwater self-healing performance, high\nsensitivity, and strong adhesion (in air and water) by using vegetable\ntannin, promoting the underwater application of sensors and the diversified\nutilization of vegetable tannin.