Harnessing acoustic energy with liquid metal triboelectric nanogenerators: A promising approach for moving-parts-free power generation

A heat-driven acoustic engine acts as a pressure source that generates oscillating acoustic waves in the presence of a working gas (typically, He or N2). These acoustic pressure waves drive a liquid metal (i.e., mercury), to slide back and forth within a U-shaped tube. As the liquid metal slides in and out of the tube, it interacts with a triboelectric generator (TEG) plate. The sliding motion of the liquid metal results in it making and breaking contact with the surface of the TEG plate. This changing contact between the sliding liquid metal and the TEG plate causes electrical charges to build up, thereby generating an electrical current. In essence, the heat input to the acoustic engine creates oscillating gas pressure waves, which drive an oscillating liquid metal flow that couples with the TENG plate to produce electricity. [Display omitted] •A fully integrated power generation system without solid moving parts is proposed.•Examines potential of Liquid metal-TEG for acoustic-to-electric conversion in TAHEs.•LM-TEG experiments are conducted in atmospheric and pressurized gas environments.•Acoustically driven LM-TEG achieves a charge density of 388 μC/m2. Heat-driven acoustic engines (HDAEs) offer a promising approach to energy generation without solid moving parts. However, integrating linear alternators for acoustic-to-electric conversion introduces moving components, diminishing this advantage. To tackle this issue, we investigate using an acoustically-driven liquid–metal triboelectric generator (LM-TEG) within HDAEs for acoustic-to-electric conversion. Experiments were conducted in three settings: mechanically-driven LM-TEGs under atmospheric and pressurized gas conditions, and acoustically-driven LM-TEGs. Results from mechanically-driven LM-TEG tests show that using FEP material, increasing LM-TEG contact area, stacking TEGs in parallel, and using pressurized gas enhance performance. Acoustically-driven LM-TEG experiments demonstrate significant improvements with pressurized nitrogen, achieving a short-circuit current approximately 4.5 times higher than with helium at equivalent pressures. Notably, charge and power densities reached 388 μC/m2 and 1.7 W/m2, respectively, surpassing typical values from conventional TEGs. Importantly, these results were obtained with a complete, fully integrated acoustically driven LM-TEG system. This study represents the first investigation in the literature of acoustically driven LM-TEGs, offering a distinct power ge