One-Step Preparation of a Highly Stretchable, Conductive, and Transparent Poly(vinyl alcohol)-Phytic Acid Hydrogel for Casual Writing Circuits.

Conductive hydrogels have shown great potential applications in a wide variety of fields, including artificial intelligence devices and biomedical engineering. However, it still remains a great challenge to develop a facile and cost-effective approach to achieve a conductive hydrogel with favorable qualities. Herein, we have changed the traditional ingredient of poly(vinyl alcohol) (PVA) hydrogel by the addition of phytic acid (PA), which could yield a conductive hydrogel through one freeze-thaw cycle. The PVA-PA hydrogel holds several virtues including a large stretchability (about 1100% strain), excellent conductivity (1.34 kΩ cm), and high optical transparence (about 95%). By assembling the PVA-PA hydrogel into a wearable strain sensor, the gel-based sensor has shown good performance for the real-time monitoring of human daily activities and health conditions. Moreover, one formula of the PVA-PA sol ink could rapidly convert to the gel state just by being injected on a flexible substrate under an ice-bath, which would satisfy the demand of casual writing circuits. This one-step preparation method of the PVA-PA hydrogel may open an innovative avenue for the fabrication of easy-molding and functional hydrogels with only two components under mild ambient conditions.