Effect of Sodium Alginate Modification on Low-Temperature Strain-Sensing Properties of Liquid Metal Hydrogel

Developing conductive hydrogels with excellent low-temperature strain-sensing properties is still a challenge. In this study, sodium alginate (SA) is used as a modifier for liquid metal (LM) to construct a double network conductive hydrogel using physicochemical cross-linked quaternary ammonium salts of chitosan and core–shell LM@SA composite. The effect of sodium alginate modification on the low-temperature strain-sensing properties of liquid metal hydrogel was studied. The results show that it leads to good stretchability (stress: 1.13 MPa, strain: 382%) and strain sensing sensitivity (GF: 3.66) of composite hydrogel prepared by adding 0.3 wt % of SA. Interestingly, adding 0.3 wt % of SA is beneficial for the low-temperature (minimum temperature: −40 °C) strain-sensing enhancement of the hydrogels, which is attributed to the supercooling effect of LM by promoting the dispersion into droplets with small particle size and the reduction of the free water content by forming the hydrogen bonds between molecules. The composite hydrogel can be used as a flexible strain sensor with the ability to monitor human activities over a wide operating temperature range and as a flexible keyboard. Overall, the study presented here provides a approach for antifreezing hydrogels that can be used for wearable strain sensors.