Dynamics and topology optimization of piezoelectric fans

Piezoelectric fans are very low power, small, very low noise, solid-state devices that have recently emerged as viable thermal management solutions for a variety of portable electronics applications including laptop computers, cellular phones and wearable computers. Piezoelectric fans utilize piezoceramic patches bonded onto thin, low frequency flexible blades to drive the fan at its resonance frequency. The resonating, low frequency blade creates a streaming airflow directed at key electronics components. The optimization of a piezoelectric fan with two symmetrically placed piezoelectric patches is investigated through an analytical Bernoulli-Euler model as well as a finite element (FE) model of the composite piezo-beam. The closed form analytical solution is used to demonstrate that different optimal piezoceramic-to-blade length ratios and piezoceramic-to-blade thickness ratios exist for maximizing the electromechanical coupling factor (EMCF), tip deflection and rotation. Such optimization procedures provide simple design guidelines for the development of very-low power, high flow rate piezoelectric fans.