A highly conductive hydrogel driven by phytic acid towards a wearable sensor with freezing and dehydration resistance

Abstract

Conductive hydrogels with anti-freezing and moisturizing properties have attracted huge attention for application in flexible electronics, which can work stably in harsh environments. However, it is challenging and urgent to enhance the environmental adaptability of hydrogels, while maintaining high conductivity. Here, a highly conductive hydrogel featuring remarkable freezing resistance and moisture-holding ability is fabricated via incorporating phytic acid (PA) into polyacrylamide/chitosan hydrogels. The addition of PA not only endows the hydrogels with a marvelous conductivity of 0.105 S cm⁻¹ due to the ionization of PA, but also promotes their antibacterial properties against Gram-negative bacteria and Gram-positive bacteria. Besides, based on the strong hydrogen bonding between PA and water molecules, the hydrogels exhibit excellent flexibility and great conductivity (0.041 S cm⁻¹) at −20 °C and could function well after storage for 15 days under ambient conditions. More importantly, the hydrogels can serve as reliable electrodes for electrocardiography (ECG) signal detection. Meanwhile, with the imperceptible strain perceivability (0.1% of strain) and a high gauge factor of 10.87, the hydrogel wearable sensors are capable of precisely monitoring and recognizing both drastic and subtle human motions under diverse working environments. This work provides a novel and promising method for developing flexible wearable electronics with environmental stability.