Date of download: 11/13/2017 Copyright © ASME. All rights reserved. From: On the Role of Nonlinearities in Vibratory Energy Harvesting: A Critical Review and Discussion Appl. Mech. Rev. 2014;66(4):040801-040801-23. doi:10.1115/1.4026278 Figure Legend: (a) Voltage and (b) power frequency response curves obtained via bidirectional frequency sweeps in two MEMS electrostatic energy harvesters with two-sided stoppers as reported by (a) Hoffmann et al. [106] and (b) Le et al. [107]. Part (a) is adapted from “Fabrication, Characterization and Modeling of Electro-static Micro-generators,” by Hoffmann et al., 2009, Journal of Micromechanics and Microengineering, 19. Reproduced by permission of IOP Publishing. All rights reserved. Part (b) is adapted from “Microscale Electrostatic Energy Harvester Using Internal Impacts,” by Le et al., 2012, Journal of Intelligent Material Systems and Structures, 23. Reproduced by permission of SAGE Publishing. All rights reserved.