Output characteristic of thin-film flexible piezoelectric generator with pure bending deformation via pneumatic energy excitation

Various flexible piezoelectric generators based on thin films are increasingly popular due to their high flexibility and long service life. Insufficient output power is the crucial problem restricting the application of flexible piezoelectric generators, whose piezoelectric capability usually depends on large strain deformation. Pure bending deformation is the primary method to give full play to its piezoelectric performance. This study demonstrates the output characteristics of a thin-film flexible piezoelectric generator under pure bending deformation via pneumatic energy excitation. The induced stress and output voltage of a flexible piezoelectric generator under different bending deformations are simulated by the finite element method (FEM) and verified by experiments. The output characteristics of a flexible piezoelectric generator with different parameters are studied, including the substrate position, the pre-bending, the velocity, the bending displacement, the aspect ratio of polyvinylidene fluoride (PVDF) film, and the thickness of the substrate. When the substrate thickness is 0.25 mm, and the PVDF aspect ratio is close to 0.6, the output performance of the flexible piezoelectric generator is better. The concept of direct current (DC) average power is proposed for the first time, and its power characteristics and load characteristics at different frequencies are studied. The peak and average power of the 8 stacked piezoelectric units in parallel can reach 4.45 mW and 0.686 mW at 6 Hz. This study can provide essential guidance for understanding the output characteristics of flexible piezoelectric generators with pure bending deformation, and promote their application in the field of pneumatic system energy capture.