Jie Wang,Jie Li,Wenfeng Luo,Qi Liu,Chen Wang,Bing Ren,Yang Cao,Jing Han,Yingchun Li
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.
Sodium acetate trihydrate (SAT) with a working temperature of about 58 °C is a significant working medium in thermal energy storage and solar energy utilization. However, supercooling effect inevitably hinders its heat release in practical applications. Typically, nucleating agents can effectively eliminate the supercooling of SAT. A concomitant problem is that the nucleating agent addition reduces the thermal energy storage capacity. In this work, a state-of-the-art methodology is constructed to eliminate the supercooling and preserve the thermal energy storage capacity of SAT synchronously by utilizing the sodium dihydrogen phosphate dihydrate (SDPD) as a novel nucleating agent. The supercooling of SAT can be reduced from 34.8 °C to 0 °C when increasing the SDPD content from 0% to 1.2%. The corresponding latent heat is slightly increased from 227.30 Jg -1 to 248.77 Jg -1 . Thermal conductivity is maintained at a relatively high level of 0.6 Wm −1 K −1 . Polypyrrole (PPY) with strong solar absorption is assembled with the SAT/SDPD composites to realize the solar energy harvesting . Taking the advantages of the functional components, the proposed SAT/SDPD/PPY device is applied in personal thermal management and the thermoelectric power generation to produce thermal comfort and clean electric energy by the solar-thermal conversion, thermal energy storage and thermal energy utilization. This work provides a new strategy for manufacturing advanced inorganic PCMs and paves the way for the application of inorganic PCMs toward solar energy utilization.
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