Flexible PZT/aluminium thin films characterizations for energy harvesting at very low frequencies (∼ 1 Hz)

With the objective to harvest the airflow energy, flexible PbZrTiO₃(PZT) thin films have been deposited onto ultra thin aluminium (Al) foil (16 μm).The piezoelectric properties of a PZT/aluminium cantilever have been investigated, and the measurements show d₃₁ values around 30 pm/V. Due to use of a very lightweight substrate, a very large deflection (in the millimeter range) of the tip of the beam have been observed, which is very promising for actuators applications. In a next step, PZT/aluminium films have been encapsulated with laminated polyethylene terephthalate (PET) in order to increase the flexibility of the device. The obtained structures were subjected to sinusoidal stress at very low frequencies (0.3 to 8 Hz) and the output voltages across a resistive load have been measured and compared to the theory with a good agreement. In addition, an intermediate ruthenium dioxide (RuO₂) layer has been used at the PZT/aluminium interface and its influence on the piezoelectric properties and the harvested power has been demonstrated.