In this work, we demonstrate mechanically flexible extremely thin silicon on insulator (ETSOI) ring oscillators with a stage delay of similar to 16 ps at a power supply voltage of 0.9 V. Extensive electrical analyses of the flexible ETSOI devices reveal the unchanged properties of the devices during the layer transfer process. Furthermore, we discuss the use of flexible silicon and gallium arsenide photovoltaic energy harvesters for powering flexible ETSOI ring oscillators under different illumination conditions. Our results illustrate innovative pathways for the implementation of optically powered flexible ETSOI technology in future flexible hybrid electronics. (C) 2015 Elsevier Ltd. All rights reserved.