Zwitterionic Hydrogel with High Transparency, Ultrastretchability, and Remarkable Freezing Resistance for Wearable Strain Sensors

Abstract

Multifunctional hydrogel with outstanding conductivity and mechanical flexibility has received enormous attention as wearable electronic devices. However, fabricating transparent, ultrastretchable, and biocompatible hydrogel with lowtemperature stability still remains a tremendous challenge. In this study, an ultrastretchable, highly transparent, and antifreezing zwitterionic-based electronic sensor is developed by introducing zwitterionic proline (ZP) into gellan gum/polyacrylamide (GG/ PAAm) double network (DN) hydrogel. The existence of ZP endows the hydrogel with remarkable frost resistance. The toughness and transparency of zwitterionic Ca-GG/PAAm-ZP DN hydrogel can be maintained down to −40 °C. Also, the zwitterionic hydrogel shows good biocompatibility and protein adsorption resistance. The zwitterionic Ca-GG/PAAm-ZP DN hydrogel-based strain sensor can accurately monitor human motions (such as speaking and various joint bendings) under a broad temperature range from −40 to 25 °C. The zwitterionic Ca-GG/PAAm-ZP DN hydrogel-based strain sensor will be of immense value in the field of wearable electronic devices, especially for extreme environment applications.

Molecularly Engineered Zwitterionic Hydrogels with High Toughness and Self-Healing Capacity for Soft Electronics Applications

“…Differential scanning calorimetry (DSC) measurement of the VBIPS hydrogel shows an exothermic peak at ∼0 °C during the cooling process because of the formation of ice crystals. In contrast, the freezing point of the VBIPS ionogel cannot be detected within the temperature range from −50 to 25°C because the ions will inhibit the freezing of water (Figure d). − Although the conductivity of the gel will decrease to some extent at low temperatures, it still maintains a relatively good conductivity at −50 °C (Figure e). The ionogel can be twisted and light a light-emitting diode (LED) even at −20 and −50 °C (Figure f).…”

Multi‐Network Poly(β‐cyclodextrin)/PVA/Gelatin/Carbon Nanotubes Composite Hydrogels Constructed by Multiple Dynamic Crosslinking as Flexible Electronic Devices

“…The high GF value was comparable to those of recently reported hydrogelbased strain sensors. [76][77][78][79][80][81][82][83] The two different GF values are able to be interpreted according to the tunneling influence and contactresistance effect. [84][85][86] When low strain is applied, carbon nanotubes in the hydrogel sensor are close to each other, and the inter-contacted parts between carbon nanotubes would be reduced with the increase of strain, leading to the improvement of tunneling and contact resistance.…”

Highly Stretchable, Adhesive Ionic Liquid-Containing Nanocomposite Hydrogel for Self-Powered Multifunctional Strain Sensors with Temperature Tolerance

“…Freezing at low temperatures and evaporation at high temperatures or long-term storage are unavoidable problems in the practical application of hydrogel materials. , High water content in a hydrogel network provides many advantages and causes some defects at the same time. The water formed into ice crystals when the traditional hydrogel was placed at a subzero temperature, resulting in large changes of hydrogel sensor in mechanical flexibility, morphology, and sensing performance .…”