Wei Li,Yang Ming,Libing Yang,Yimeng Ni,Yu Chen,Weidong Xu,Lefei Li,Chan Zheng,Wanyang Lin
Hydrogels with conductive properties hold significant promise in the realm of flexible electronics, owing to their pliability, outstanding conductivity, and diverse functionalities. Nevertheless, the majority of conductive hydrogels are prone to being brittle and easily damaged; as such, they are not adapt to cold environments, which seriously hinders their practical applications. Therefore, hydrogels that possess both conductivity and anti-freezing, as well as moisturizing, capabilities have garnered considerable interest, and these hydrogels can work stably in harsh environments. Phytic acid (PA), which mainly exists in plant seeds, is a kind of natural compound widely existing in nature that can be recycled; it provides electrical conductivity and anti-freezing to hydrogels. Here, a highly conductive hydrogel with excellent anti-freezing and moisturizing capabilities was prepared by incorporating PA into a polyacrylamide/gelatin hydrogel. The incorporation of PA endowed the hydrogel with an excellent conductivity of 5.8 S·cm−1. In addition, robust hydrogen bonding was formed between water and phytic acid molecules, and the hydrogel demonstrated remarkable anti-freezing and water retention. On this basis, hydrogels can be used for human winter sports sensing and low-temperature environmental alarm devices to provide faster rescue. This study provides a novel method for the development of hydrogels with low-temperature stability, and provides a revelation for the application of anti-freezing hydrogels in icy and snowy environments.
Xinpeng Lv,Qiwei Zhang,Ze Li,Kai Gong,Bing Gao,Hongqiu Wei,Peng Li
Conductive hydrogels are promising for flexible electronic device applications, where strain change is converted to electrical signal responses. However, most reported conductive hydrogels are typically frozen around 0°C and dried out limiting their potential applications. Herein, a highly stretchable ionic conductive hydrogel (ICH) with antifreezing and water retention properties was prepared using a natural polymer-based hydrogel (sodium alginate-co-polyacrylamide) as the matrix material. By introducing highly hydrated salt CaCl 2 and ethylene glycol via a solvent displacement method, the ICH exhibits high ionic conductivity (0.91S/m at 20°C), high transparency (95%), and antifreezing properties (−43°C). Moreover, the optimized ICH achieves a satisfactory sensitivity toward tension strain (gauge factor = 2.58 at 100% strain). Interestingly, a real-time sensing system for wearable motion based on the resulting ICH is well developed by integrating a wireless transmission platform. It is anticipated that such an ICH sensing system will significantly broaden the opportunities for flexible sensor applications.
Yutong Yang,Hao Sun,Chenghao Shi,Yuxuan Liu,Yachong Zhu,Yongming Song
Hydrogels are widely used as sensors in the field of wearable devices. However, the hydrogels were rarely designed to endure the harsh outdoor environment in winter, including extremely low temperature, ultraviolet (UV) radiation and variable humidity. In addition, physical damage is also a challenge for hydrogels. In this study, a self-healing hydrogel with adhesion was prepared as a sensor for winter sports using a one-pot method. Polyvinyl alcohol was used as the hydrogel matrix, providing the hydrogel preferable self-healing properties and adhesion to various surfaces such as porcine skin, metal, glass, and plastic. Lithium chloride was used for the chain entanglement of polyvinyl alcohol, forming a hydrogel with excellent ionic conductivity (24.29 S m −1 at room temperature, 13.45 S m −1 under −18 ℃) to detect human motion and temperature changes. Together with ethylene glycol, lithium chloride also provided successful water retention ability and frost resistance. The hydrogel remained stable after 30 d of storage at room temperature and −18 ℃. Sodium lignosulfonate was introduced to improve the mechanical properties and ultraviolet (UV) resistance of hydrogel, created nearly 100% UV shielding with a thickness of 0.5 mm. These advantages provide great potential to the hydrogel for application in flexible wearable devices for winter sports.
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