Tough, Adhesive, and Ionically Conductive Hydrogels via Digital Light Processing 3D Printing as Wearable Sensors

Abstract

Photocurable, 3D-printable conductive hydrogels hold great promise for personalized wearable sensors and flexible bioelectronic devices. However, current systems still face challenges in simultaneously achieving printability, mechanical robustness, electrical conductivity, and interfacial adhesion. In this study, an ionically conductive hydrogel system based on poly(vinyl alcohol) (PVA), polyacrylamide (PAM), tannic acid (TA), and glycerol (Gly), denoted as PATG, was fabricated by digital light processing (DLP) 3D printing. The hydrogel exhibited excellent mechanical properties, including a fracture strain of 480%, a tensile strength of 271 kPa, and a tensile toughness of 550 kJ m–3. It also achieved a compressive toughness of 90 kJ m–3 at 90% compressive strain and maintained structural stability after 100 compression cycles. Furthermore, the PATG hydrogel showed an electrical conductivity of 1.082 S m–1 and a segmented linear response over 0–480% tensile strain, with a maximum gauge factor of 13.73. Benefiting from its stretchability and ionic conductivity, PATG enabled reliable monitoring of joint motion, finger bending, and Morse code input, while its adhesion and antibacterial properties support skin-attached wearable applications. As a flexible electrode, PATG recorded electrocardiogram (ECG) and electromyography (EMG) signals with signal-to-noise ratios (SNRs) of 32.62 and 14.73 dB, respectively, showing signal acquisition capability comparable to that of commercial electrodes under the tested conditions. This work provides a multiple-network strategy for constructing personalized hydrogel-based wearable devices.