A triple-crosslinked, self-healing, polyvinyl alcohol/nanocellulose hydrogel for versatile sensing applications

Flexible conductive hydrogels (FCHs) have attracted widespread interest as versatile monoliths that can be intricately integrated with various ingredients boasting multiple functionalities. The chemicophysical properties of FCHs cover a wide range, which significantly vary in their building blocks. However, achieving both favorable mechanical strength and high conductivity simultaneously through a facile approach remains a challenge. Herein, polyvinyl alcohol, dialdehyde cellulose nanofibrils, silver nanoparticles, borax, and tannic acid are readily "one-pot" incorporated into FCHs with great tensile stress (499 kPa), tensile strain (4591 %), and compressive stress (269 kPa) due to abundant hydrogen bonding, dynamic borate-diol bonding, and intermolecular acetalization. They also exhibit desired self-healing, generalized-adhesive, and antibacterial performances. Taking advantage of these, FCHs are further employed to support an epidermal sensor, on which remarkable strain sensitivity (gauge factor = 8.22), high-pressure sensitivity (≥ 0.258 kPa^-1), and fast response (≤ 190 ms) are recorded. Its highly adaptive mechano-electric transformability and functions can be well maintained in serving as an array unit and touch screen pen. The results well addressed in this work are anticipated to pave the universal way of engineering FCHs.