Design high ductility and self-adhesion ionic hydrogel for strain sensors using polyacrylamide and gum arabic

Robust adhesion is crucial for ionic hydrogels in flexible electronic pressure and strain sensors. Herein, we design a transparent and strong adhesion electronic pressure and strain sensor based on a multifunctional ionic hydrogel with double network using polyacrylamide (PAM) and gum arabic (GA). First, the effect of ionic type on the mechanical properties of hydrogels was measured. The GA/PAM–Fe³⁺ hydrogel with high extensibility (1835%) and toughness \(\left( {{1}.{\text{47 MJ}}/{\text{m}}^{{3}} } \right)\) $\left(1.\text{47 MJ}/{\text{m}}^3\right)$ was selected as the best sensor material. Moreover, the GA/PAM–Fe³⁺ hydrogel has good adhesion property with various substrates, and the maximum peel strength of the hydrogel to skin could reach up to 123.9 N/m. Furthermore, the resistance of GA/PAM–Fe³⁺ hydrogel is sensitive to a wide strain window and the gauge factor shows stable and reliable change during deformation. Due to its compliant and excellent adhesive properties, strain sensors based on this hydrogel can be well fixed on the epidermis without adhesive tape, and can perceive large and gentle body movements. These characteristics demonstrate that GA/PAM–Fe³⁺ hydrogel is promising for a broad range of practical applications in wearable sensors.