Integration of PZT thick films on additively manufactured substrates for vibrational energy harvesting applications

Abstract

This work aims to integrate screen-printed thick film (50–100 µm) Pb(Zr,Ti)O3 (PZT) on additively manufactured stainless steel substrates for vibration energy harvesting. The manufacturing technologies advanced by this research opens new horizons for energy harvesting applications as it standardizes the development and manufacturing processes, thereby making vibration energy harvesters more feasible. Since the parts are built layer-by-layer, the thickness of the different layers of the substrate can be controlled. The substrates under study were manufactured using SLM (Selective Laser Melting) additive manufacturing technology from Stainless Steel 17-4 PH powder. Simple cantilever harvesters are chosen as an initial target to focus on the optimization of the screen-printing process. The sample is 15.6 mm long, 4.1 mm wide, and 0.35 mm thick cantilever beam with a 50 µm thick PZT screen-printed layer sandwiched between two gold electrodes. A dielectric layer printed on the stainless steel substrate was introduced to promote adhesion. Clamping 6.1 mm of the beam length, its resonant frequency was measured experimentally at ∼2 kHz. The maximum output power was 37 nW under a resonant base acceleration with an amplitude of 2.94 m/s2 and a load resistance of 90 kΩ. A good fit was found between the experiment and a Finite Element Model with a difference of 12%. Thermal stress analysis was carried out to study the impact of the difference of Coefficient of Thermal Expansion on the bending of the harvester and the adhesion between the layers. The result shows the importance of matching the Coefficient of Thermal Expansion of the substrate with that of the PZT layer to avoid delamination between the layers and to improve adhesion. These initial results open routes for optimized designs of printed piezoelectric energy harvesters.