Jiaqing Xiong1 Meng-Fang Lin1 Jiangxin Wang1 Sheng Long Gaw1 Kaushik Parida1 Pooi See Lee1

1, Nanyang Technological University, Singapore, , Singapore

Wearable energy harvesting devices are greatly attractive and receive intensive research efforts in recent years, aiming at powering various emerging flexible and wearable electronics, such as smart clothing, eye glasses, wristwatches, and even healthcare sensors. So far, inflexible rigid plate is the typical form of energy harvesting and storage, although some thin film-shaped power systems have been designed to achieve flexible or stretchable energy devices, the film structure could not be twisted freely or deformed extensively to fully satisfy the requirements of wearable electronic devices. To this end, a lot of efforts were made to explore the fiber/fabric based device, attempting to promise wearable energy devices. Rainwater, ocean waves and waterfalls are sources of clean energy which is almost inexhaustible, renewable and not limited by daylight. Moreover, the flowing water not only carries mechanical energy, but also produces triboelectricity due to contact electrification process with air or other substrates.
Realizing energy harvesting from water flow using triboelectric generators (TEGs) based on our daily wearable fabric or textile has practical significance. Challenges remain on the methods to fabricate conformable TEGs that can be easily incorporated into waterproof textile, or directly harvest energy from water using hydrophobic textiles. In this work, we developed for the first time a wearable all-fabric-based TEGs for water energy harvesting, with additional self-cleaning and antifouling properties. Hydrophobic cellulose oleoyl ester nanoparticles (HCOENPs) were prepared from microcrystalline cellulose (MCC), as a low-cost and nontoxic coating material to achieve superhydrophobic coating on fabrics, including cotton, silk, flax, polyethylene terephthalate (PET), polyamide (Nylon) and polyurethane (PU). The resultant PET fabric based water-TEG (WTEG) can generate an instantaneous output power density of 0.14 W m-2 at a load resistance of 100 MΩ. An all-fabric-based dual-mode TEG (DMTEG) was further realized to harvest both the electrostatic energy and mechanical energy of water, achieving the maximum instantaneous output power density of 0.30 W m-2. The HCOENPs coated fabric provides excellent breathability, washability and environmentally friendly fabric-based TEGs, making it a promising wearable self-powered system.