Fabricating and Engineering Woody-Biomass Aerogels for High-Performance Triboelectric Nanogenerators for Energy Harvesting and Biomechanical Monitoring

Woody biomass is an abundant renewable resource. In this study, aerogels for versatile triboelectric devices are fabricated from poplar biomass via a dissolution-and-regeneration method with concentrated lithium bromide solution as the solvent. To improve the aerogels' structural homogeneity, two treatments—ball-milling the raw poplar woody biomass before its dissolution, and, separately, ultrasonication following its dissolution—were applied. These treatments altered the porous structures and mechanical properties of the resulting aerogels, leading to a marked increase in their triboelectric performance. Removing the majority of the lignin from the aerogels was also explored, and resulted in triboelectric output ≈5 times greater than that of pristine woody biomass aerogel (i.e., without ball milling, ultrasonication, or lignin reduction). The underlying mechanisms of such increases were found to be both chemical and physical. Next, triboelectric devices were fabricated using the optimal (i.e., low-lignin) aerogel for energy harvesting and biomechanical monitoring. These devices were able to: 1) respond sensitively to force, likely due to the aerogel's porous structures; 2) capture mechanical energy, charge capacitors, and power small portable electronics; and 3) monitor biomechanical movements including respiration, joint motions, and gait-pattern changes.