3D printable ionically conductive cellulose hydrogel sensor with robust water binding property at low temperatures

Abstract

Conductive hydrogel sensors are pivotal for next-generation flexible wearable devices. However, conventional hydrogels suffer from limitations such as insufficient low temperature tolerance, mechanical robustness, and biocompatibility. Herein, a binary molten salt hydrate (MSH) consisting of zinc chloride (ZnCl₂) and lithium bromide (LiBr) has been found to efficiently dissolve natural cellulose for synthesis of ionically conductive hydrogel with robust water binding property. The conductive cellulose hydrogel achieved surpassing ionic conductivity of 4.48 S/m, impressive compressive strength of 2.48 MPa, and excellent sensing performance. Molecular simulations disclosed the synergistic effect of lithium and zinc ions in cellulose dissolving and stabilization of the cellulose solution by forming robust water binding performance under low temperatures. Differential scanning calorimetry (DSC) analysis revealed no exothermic peaks associated with water crystallization over the temperature range from −80 to 20 °C. Furthermore, shear-thinning characteristics of the conductive hydrogel under room temperature make it 3D printable for fabricating customized complex geometries. This work provides a binary molten salt system for facile processing of flexible wearable sensors from cellulose with mechanical robustness, biocompatibility.

Keywords

Ionically conductive cellulose hydrogel / Molten salt hydrate / Wearable flexible sensor / Anti-freezing

References

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