Low-temperature resistant hydrogel with inkjet-printed MXene on microspine surface for pressure sensing and triboelectric energy harvesting

Wearable, flexible sensors based on hydrogel fabrication have recently gained significant attention due to their unique properties. However, developing hydrogel sensors that maintain high sensitivity and work effectively in sub-zero temperatures remains a formidable challenge. Herein, a hydrogel with surfaces featuring randomly distributed microspines is synthesized by combining sodium alginate (SA) and acrylamide (AM) as the hydrogel components. To fabricate a wearable sensor, a highly conductive MXene layer is inkjet-printed onto the surface of the hydrogel microspines. The resulting sensor exhibits a remarkable array of features, including exceptional sensitivity (15.03 kPa⁻¹), a low detection limit (10 Pa), a vast operating range (0.12–70 kPa), rapid response and recovery (40/100 ms), reliable performance (over 1000 cycles), and outstanding resistance to low temperatures (-20 °C). Moreover, this hydrogel-based sensor facilitates the efficient collection of human monitoring data, such as vocal patterns, pulse, and joint movements, even when operating at −20 °C and in ice bath conditions. Importantly, the surface-based inkjet MXene hydrogels could be assembled into a deformable triboelectric nanogenerator (TENG), allowing mechanical energy harvesting. The TENG exhibited peak output voltage and current values of 5 V and 2.5 μA, respectively.