Fabrication of piezoelectric vibration energy harvester using coatable PolyVinylidene DiFluoride and its characterisation

Abstract

A cantilever-type vibration energy harvester (VEH) made of PolyVinylidene DiFluoride (PVDF) was fabricated and characterised. PVDF is one of polymer piezoelectric material, which is more flexible than ceramic-based piezoelectric materials such as lead zirconate titanate. Since PVDF dissolves in organic solvent, it is coatable on substrate or parts, making it compatible with micro electro mechanical systems process. The fabrication process of VEH is as follows: a PVDF film (thickness: 30 µm) was coated on a phosphor bronze rectangular plate (length: 35 mm, width: 15 mm, thickness: 0.1 mm) by bar-coating method, followed by polarisation by corona discharge method. Aluminium top electrode (length: 30 mm, width: 10 mm, thickness: 0.3 μm) was deposited on the PVDF film by DC sputtering. One end of the plate was clamped by a fixture to form a cantilever, the length of which is 25 mm. Finally, a proof mass (m = 0.2 g) was attached to the free end of cantilever. Output power P at resonant frequency (= 55 Hz) was measured as a function of load resistance R, in which acceleration was set to 17 m/s2. Maximum output of 4.3 µW was achieved at R = 2.1 MΩ, which is not inferior to those of reported VEHs using ceramic piezoelectric materials.