Low-Cost, High-Performance Piezoelectric Nanocomposite for Mechanical Energy Harvesting

Lack of low-cost, large area deposition methods and photo-patternability of high-performance piezoelectric materials restrict the rapid development of efficient functional devices like sensors and energy harvesters. In this paper, we report an optimized process flow for Zinc Oxide (ZnO)/SU-8 and Barium Titanate (BTO)/SU-8 based nanocomposite thin films for mechanical energy harvesting (MEH) applications. Parametric variation of process variables for these nanocomposites reveals that 15% ZnO/SU-8 and 20% BTO/SU-8 nanocomposites show optimum results with good piezoelectric response and UV transmittance, allowing reliable lithography of the nanocomposites. Furthermore, three different types of energy harvesting devices are fabricated using these nanocomposites as piezoelectric layer. Output powers of
$223~\mu \text{W}$
(ZnO/SU-8) and
$642~\mu \text{W}$
(BTO/SU-8) are produced at resonance for the conventional cantilever type MEH devices at an input acceleration of 0.5g. Using the nanocomposites as flexible nanogenerator, open circuit voltages of 570 mV (ZnO/SU-8) and 780mV (BTO/SU-8) are obtained using regular finger pressing. The hybrid energy harvesters, based on combined piezoelectric-triboelectric transduction mechanisms, generate output voltages of 0.4V, 0.95V, 1.4V (ZnO/SU-8) and 0.7V, 1.1V and 1.9V (BTO/SU-8) in piezoelectric, triboelectric and hybrid operations, respectively.