Maximizing the Energy Output of Soft Electrohydraulic Generators
Sophie Kirkman, Ingemar Schmidt, Lawrence T. Smith, Steven L. Zhang, Shane K. Mitchell, Soo Jin Adrian Koh, Philipp Rothemund, Christoph KeplingerABSTRACT
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.