Ultrasensitive and Stretchable Temperature Sensors Based on Thermally Stable and Self-Healing Organohydrogels

Abstract

It is essential to impart the thermal stability, high sensitivity, self-healing, and transparent attributes to the emerging wearable and stretchable electronics. Here, a facile solvent replacement strategy is exploited to introduce ethylene glycol/glycerol (Gly) in hydrogels for enhancing their thermal sensitivity and stability synchronously. For the first time, we find that the solvent plays a key role in the thermal sensitivity of hydrogels. By adjusting the water content in hydrogels using a simple dehydration treatment, the thermal sensitivity is raised to 13.1%/°C. Thanks to the ionic transport property and water–Gly binary solvent, the organohydrogel achieves an unprecedented thermal sensitivity of 19.6%/°C, which is much higher than those of previously reported stretchable thermistors. The mechanism for the thermal response is revealed by considering the thermally activated ion mobility and dissociation. The stretchable thermistors are conformally attached on curved surfaces for the practical monitoring of minute temperature change. Notably, the uncovered Gly-organohydrogel avoids drying and freezing at 70 and −18 °C, respectively, reflecting the excellent antidrying and antifreezing attributes. In addition, the organohydrogel displays ultrahigh stretchability (1103% strain), self-healing ability, and high transparency. This work sheds light on fabricating ultrasensitive and stretchable temperature sensors with excellent thermal stability by modulating the solvent of hydrogels.

PVA/Agar Interpenetrating Network Hydrogel with Fast Healing, High Strength, Antifreeze, and Water Retention

“…The instability of traditional hydrogels at room temperature and cold conditions seriously limits the application of compliant products, which are due to the loss of water, elasticity at room temperature and freezing of water at freezing temperatures. At present, there are two main solutions to solve these problems, one is to reduce the freezing point of the system by using a solvent, [41,42] and the other is to reduce the freezing point by using an inorganic salt. [43,44] The strategy of using an EG/H 2 O binary solvent instead of a distilled water solvent endowed the hydrogel with superb anti-freezing properties.…”

Recent Progress in Self‐healing Materials for Sensor Arrays

“…(3) In hydrogels, the solvent content plays an important role in thermal sensitivity. For example, replacing part of the water in the hydrogel with molecular polyols (such as glycerol and ethylene glycol) and adjusting the water content in the hydrogel using a dehydration treatment can enhance its thermal sensitivity [195] …”

“…In an earlier study, Wu et al [195] . developed ultrasensitive and stretchable temperature sensors based on self‐healing organo‐hydrogels, which were synthesized from ethylene glycol (Eg) and glycerol (Gly).…”

Synthesis Antifreezing and Antidehydration Organohydrogels: One-Step In-Situ Gelling versus Two-Step Solvent Displacement

“…After solvent displacement, the obtained organohydrogels exhibited low temperature tolerance down to −70 • C [15]. Since then, due to its universality, solvent displacement became another popular strategy to synthesize the environment-adaptable organohydrogels [23,24,27,28,34,[40][41][42][43][44][45][46].…”