As reported previously, several paper-based NGs have shown impressive power output up to ~130 -150 µW (polymer-based NGs). To measure the voltage output changes pertaining to the curvature of the substrate (strain based), bending experiments were performed on the Mn3O4membrane-based device. The variation in output voltage was observed to be linear as bending angle changes without application of external pressure. A maximum output voltage (Voc) of 1.3 and 1.8 V (peak to peak voltage) was obtained for 30° and 50° bend, respectively (Figure ).