Tara Tannin-Cross-Linked, Underwater-Adhesive, Super Self-Healing, and Recyclable Gelatin-Based Conductive Hydrogel as a Strain Sensor

Abstract

Conductive hydrogel strain sensors have triggered extensive research interest in artificial intelligence, human motion detection, electronic skin, and other technical fields. However, it is still challenging work to prepare conductive hydrogels integrated with good biocompatibility, recyclability, selfhealing, and strong adhesion properties both in air and underwater. Herein, a novel, ultraexcellent self-healing, adhesive, and multifunctional gelatin composite hydrogel was fabricated through a simple and rapid one-pot method in which gelatin (Gel) and polyvinyl alcohol (PVA) were used as the polymeric skeletons, Tara tannin as the cross-linking agent, and multiwalled carbon nanotubes (CNTs) as the conducting medium. Inspired by the vegetable tanning mechanism in tanning chemistry, the multiple hydrogen bonding and hydrophobic interactions of Tara tannin with Gel were used to build the crosslinking network of the hydrogel. The obtained GTPC (Gel-Tara tannin-PVA-CNTs) hydrogel exhibited considerable stretchability (760%), strong adhesion strength (16 kPa to pigskin), and high conductive sensitivity (gauge factor (GF) = 6.79). In particular, the GTPC hydrogel displayed good repeatable adhesion (≥10 times) and rapid self-healing performance (HE (self-healing efficiency) > 99%) both in air and underwater. The formed GTPC hydrogel strain sensor could accurately detect various motion signals, such as finger bending, ankle bending, and smiling, and it could also sensitively capture sensing signals of body movements underwater. The self-healed hydrogel sensor also exhibited a similar motion sensing ability to the original one. This work affords a new idea and method for the design and fabrication of flexible strain sensors with rapid air and underwater self-healing performance, high sensitivity, and strong adhesion (in air and water) by using vegetable tannin, promoting the underwater application of sensors and the diversified utilization of vegetable tannin.

3D Printable Self-Adhesive and Self-Healing Ionotronic Hydrogels for Wearable Healthcare Devices

“…The GF and linearity ( R 2 ) in the middle strain range (600–1400%) were 1.2 and 0.9912, respectively, while those in the high strain range (1400–2000%) were 2.5 and 0.9907, respectively. The response and recovery times of the PPT hydrogel were approximately 0.5 and 0.6 s, respectively (Table S2), which are comparable to those of other hydrogel-based strain sensors. , The PPT hydrogel sensor also showed stable signals during the 100 cycles of repeated strain tests (Figure S9).…”

“…The response and recovery times of the PPT hydrogel were approximately 0.5 and 0.6 s, respectively (Table S2), which are comparable to those of other hydrogel-based strain sensors. 47,48 The PPT hydrogel sensor also showed stable signals during the 100 cycles of repeated strain tests (Figure S9).…”

Collagen-Based Organohydrogel Strain Sensor with Self-Healing and Adhesive Properties for Detecting Human Motion

“…Recently, flexible conductive sensors were increasingly investigated owing to their tremendous applied value in human–computer interaction, − electronic skin, − soft robots, , and health monitoring. − Conductive hydrogels, as a kind of conductive soft materials, have attracted much research interest due to their excellent flexibility, conductivity, lightweight, and other attractive characteristics. − The ideal conductive hydrogel-based flexible sensor is expected to possess multi-environmental applicability; thus, it can be applied in different real environments, such as warm, cold, and even underwater conditions. However, most of the current reports have mainly focused on the anti-freezing performance of conductive hydrogels.…”

Multifunctional MXene Conductive Zwitterionic Hydrogel for Flexible Wearable Sensors and Arrays

“…The zwitterionic hydrogels based on PSM/TF/Zn 2+ -40 wt % have good sensitivity and frost resistance with self-adhesive properties and good water retention. In order to demonstrate its potential usefulness in biomonitoring, we connected the zwitterionic hydrogel with an electrochemical workstation, assembled it into a flexible wearable sensor, and attached it to different parts of the body (face, fingers, elbows, knees, etc., Figure a) for real-time detection of complex physical activities and subtle facial expressions. − It included small movements, for instance, frowning, smiling, and slight finger movements, as well as changes in relative resistance to larger movements, such as lowering the head, bending the back of the hand, making a fist, pressing, bending of the elbow, walking, jumping, and squatting (Figure b–m). It can be seen that the zwitterionic hydrogel sensors have sensitive strain capacity, and the PSM/TF/Zn 2+ -40 wt % zwitterionic hydrogel sensor can detect changes in the signal even at low temperatures, displaying immediate signal capture capability, fast response, and high robustness (Figure S23).…”