Energy harvesting efficiency of a quasi-zero stiffness energy harvester Jerzy Margielewicz, Damian Gąska, Grzegorz Litak, Piotr Wolszczak and Shengxi Zhou Eur. Phys. J. Spec. Top., 231 8 (2022) 1557-1565 Published online: 20 March 2022 DOI: 10.1140/epjs/s11734-022-00500-1