Maximizing the Energy Output of Soft Electrohydraulic Generators.

Energy harvesting from ocean waves and human motion remains largely unused, despite vast potential. Soft electrostatic transducers are a potential solution, leveraging shape-dependent capacitance to convert mechanical energy into electricity. While hydraulically-amplified self-healing electrostatic (HASEL) transducers are versatile, high-performance actuators, their potential as generators remains largely unexplored. Through a combined theoretical and experimental approach, this work elucidates how to maximize the energy output of HASEL generators: a quasi-static analytical model explains the fundamental mechanisms governing the behavior of the generators and enables mapping of their operational limit-states on work-conjugate planes; a comprehensive parametric evaluation confirms that the model captures key experimental trends, allowing for the construction of a roadmap toward generators with substantially increased performance. Notably, this work reveals a compressive force causes greater capacitance change and higher electrical energy output than the same force in tension. Guided by the model, the optimized generator design and operating conditions lead to a maximum specific energy and power of 15 J/kg and 43 W/kg, and energy conversion efficiency of 40%, setting new benchmarks in all measured metrics. Built on a foundation of rigorous theoretical and experimental analysis, the roadmap will guide the development of high-performance electrohydraulic generators for capture of underutilized energies.