The schematic diagrams of the fabrication process are shown
in Figure 1 a and detail information described in Experimental
section. Figures 1 b and c show cross-sectional scanning electron
microscopy (SEM) images of a 250 μ m thick p-NC that is
sandwiched between the top and bottom metal-coated plastic
substrates. A magnifi ed cross-sectional SEM image (Figure 1 c)
shows that the BaTiO 3 NPs and the MW-CNTs are well distributed
in the PDMS matrix. The BaTiO 3 NPs generate piezoelectric
potential under external stress and act as an energy generation
source. The CNT’s role in an NCG device as dispersant,
stress reinforcing agent, and conducting functional material is
explained later. The volume percentage of CNT is controlled so
low so that they do not affect the dielectric property of the entire
structure. The hydrothermal BaTiO 3 NPs have a rounded shape
with size of 100 nm (see Figure 1 d and Figure S1a-i). Raman
analysis is conducted to provide a more comprehensive phase
characterization of the BaTiO 3 NPs (the inset of Figure 1 d). The
sharpness of the spectrum in the range of 305 to 720 cm − 1 is
ascribed to the A 1 and E (longitudinal optical) modes, which
are specifi c to a tetragonal phase of BaTiO 3 . [ 24 ] The crystalline
structure of the BaTiO 3 NPs is characterized by X-ray diffraction
(see Figure S1a-ii