Ultra-Stretchable, durable and conductive hydrogel with hybrid double network as high performance strain sensor and stretchable triboelectric nanogenerator

Hydrogels with integrated attributes of stretchability, conductivity, transparency and robustness have been emerging because of their promising applications in wearable devices, human health monitoring, advanced intelligent systems and energy harvesting. In this paper, we developed stretchable and conductive hydrogels via hybrid double networks approach by combination of rigid physically cross-linked gelatin, tough chemically cross-linked polyacrylamide (PAM) and poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) as conducting component. The double networks can be further interlocked by using physical entanglements and abundant dynamic hydrogen bonds, contributing to the improved mechanical properties and self-recovery ability. A transparent and wearable strain sensor is fabricated by sandwiching the hydrogels with two layers of adhesive polyurethane (PU) tape, exhibiting good sensitivity (gauge factor (GF) = 1.58), ultra-wide sensing range of 0-2850% strain, short response time of 200 ms and superior durability and reproducibility (1200 cycles), which endows the sensitive monitors with effective discernibility for detecting intricate human motions. Importantly, the hydrogel-based device can act as a highly stretchable (300% strain) triboelectric nanogenerator (STENG) for efficient energy harvesting, giving a short circuit current (ISC) of 26.9 μA, open circuit voltage (VOC) of 383.8 V and short-circuit transferred charge (QSC) of 92 nC. The integrated abilities of strain sensing and energy harvesting promise the hydrogels for high performance self-powered wearable devices and stretchable power sources.