Mimicking skin cellulose hydrogels for sensor applications

The soft electronics industry is booming. To integrate with soft tissues (e.g. skin), the materials must possess skin-like properties in terms of stretchability, toughness, elasticity, softness, self-stiffness, swelling resistance, and conductivity. Herein, a biocompatible cellulose biomimetic hydrogel (CBH) showing the characteristics of the skin is fabricated. The first step is the regulation of cellulose self-assembly to form a porous non-swelling supramolecular fiber skeleton. Then, the elastic polymers generate within the pores of skeleton. This design mimics the skin’s structures by utilizing the crystallization behavior of cellulose. Importantly, the cellulose supramolecular network has significantly strengthened the resultant hydrogels with over a 45-fold increase in toughness, and it could reach 4.3 MJ/m3. Moreover, it shows enhanced properties in terms of stretchability, modulus, self-stiffness and elasticity. Investigation on the swelling resistance shows that the utilization of non-swelling porous cellulose skeleton can limit the swelling of CBH. Finally, the fabrication of conductive CBH is performed through the in-situ polymerization of aniline within CBH. It can retain the mechanical features due to the tunable swelling, and also be used as a sensitive and stable strain sensor to monitor human motions, even under an aqueous environment. The gauge factor within the range of 90% to 600% was 1.7. This study highlights the significance of utilizing original cellulose features and provides a new avenue to prepare high-performance strain sensors.