Gastric fold-inspired microwrinkled carbon nanotube sheets for harvesting mechanical energy of organ motion

Biomechanical energy from daily activities and organ motion is an attractive energy source because of its sustainability. Mechanical energy harvesters, including triboelectric, piezoelectric, and chemo-mechanical harvesters, are gaining significant attention for converting energy into electrical power for self-powered devices. Chemo-mechanical energy harvesters that utilize the piezoionic effect are particularly suited for harnessing the movements of organs, such as the heart, stomach, and lungs, in the electrolyte-rich environment of the human body. However, existing harvesters are inefficient because of their unidirectional response and high modulus, which hinder organ motion. In this paper, we propose a microwrinkled carbon nanotube (CNT) sheets harvester (MCSH), inspired by the gastric wrinkle morphology and featuring a low modulus (43.9 kPa), capable of multidirectional energy harvesting. The MCSH generates energy through the relaxoionic effect during unfolding and folding cycles, achieving an open-circuit voltage change of 11.6 mV and a peak current of 112.5 A kg⁻¹ in 0.1 M HCl. Finally, the MCSH demonstrated stable energy generation in a human stomach model using simulated body fluids.