Integrated paper-hydrogel structure for spontaneous and ultra-durable eco-friendly electricity generation

Moisture-sorption-based energy harvesting emerges as a promising approach to harnessing electricity from the environment, presenting immense potential as a power reservoir for compact wearable electronic devices. Progress in water-absorbing materials has propelled the advancement of sustainable moisture energy technologies. However, challenges persist in low-humidity environments and maintaining stable outputs due to varying humidity levels. To tackle these issues, a paper-hydrogel electric generator (PHEG) was developed by integrating commercial cellulose-based filter paper and adhesive polyacrylamide (PAM) hydrogel. The PHEG generates a voltage of approximately 0.6 V through the generation and diffusion of protons within paper and the “galvanic reaction’’ facilitated by its asymmetric electrodes. This process produces a current of around 12.5 μA/cm² and delivers a power output of approximately 1.61 μW/cm². Moreover, assembling 10 PHEG units produced a battery-like power component, delivering a direct current voltage of about 6 V. The PAM gel with 50 % glycerol content enabled the device to sustain voltages > 0.4 V for over 1000 h without external stimulation. PHEG also demonstrated its potential as a self-powered strain and pressure sensor. As a green and easily deployable device combining gel and commercial papers, PHEG holds tremendous potential for eco-friendly and self-sufficient wearable electronics, offering a sustainable solution for renewable power supply.