Abstract
Conductive hydrogel is a vital candidate for the fabrication of flexible and wearable electric sensors due to its good designability and biocompatibility. These well-designed conductive hydrogel–based flexible strain sensors show great potential in human motion monitoring, artificial skin, brain computer interface (BCI), and so on. However, easy drying and freezing of conductive hydrogels with high water content greatly limited their further application. Herein, we proposed a natural polymer-based conductive hydrogel with excellent mechanical property, low water loss, and freeze-tolerance. The main hydrogel network was formed by the Schiff base reaction between the hydrazide-grafted hyaluronic acid and the oxidized chitosan, and the added KCl worked as the conductive filler. The reversible crosslinking in the prepared hydrogel resulted in its resilience and self-healing feature. At the same time, the synthetic effect of KCl and glycerol endowed our hydrogel with outstanding anti-freezing property, while glycerol also endowed this hydrogel with anti-drying property. When this hydrogel was assembled as a flexible strain sensor, it showed good sensitivity (GF = 2.64), durability, and stability even under cold condition (−37°C).
Highlights
Hydrogels with a water-rich polymer network structure are very similar to the native tissues of humans (Fergg et al, 2001; Sanchez et al, 2005)
Our conductive and antifreezing hydrogel, HC-KG hydrogel, was formed by a one-step mixing-injection between the prepared Hyaluronic acid (HA)-ADH solution and oxidized chitosan (OCS) solution with equal volume (Figure 1C), Supplementary Figure S2; Supplementary Table S1 showed that the addition of KCl prolonged gelation time greatly
The results showed that the conductivity of HC-KG hydrogels during this process was almost all in the range of 0.63 S/m
Summary
Hydrogels with a water-rich polymer network structure are very similar to the native tissues of humans (Fergg et al, 2001; Sanchez et al, 2005). Due to their flexibility, biocompatibility, and designability, hydrogels are widely utilized in various areas, such as tissue engineering (Lee and Mooney, 2001; Khademhosseini and Langer, 2007), wearable devices (Fergg et al, 2001; Yuk et al, 2019; Cui et al, 2021), and flexible electrodes (Na et al, 2019; Zhang W. et al, 2020; Fu et al, 2020). Various studies have reported that the addition of inorganic salts, such as LiCl, NaCl, KCl, and ZnCl2, into the hydrogel systems could bestow the hydrogel with satisfactory ion conductivity (Li et al, 2017, Li et al, 2019, Li et al, 2021; Jiang et al, 2018; Hou et al, 2019). G. et al, 2008; Jiang et al, 2019; Xu et al, 2021)
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