TEMPORARY PACKAGING OF PZT THIN-FILM MICROACTUATORS.

This paper is to demonstrate a temporary encapsulating technique that uses photoresist to package PZT thin-film microactuators for an experimental inner ear implant. The microactuator consists of a diaphragm suspension, a bottom electrode, a PZT thin film, and a top electrode. The dimensions of the microactuator and the diaphragm suspension are 3 mm × 3 mm × 400 μ m and 900 μ m × 900 μ m × 0.95 μ m, respectively. A layer of photoresist (AZ1512) with a thickness around 4-16 μ m is brushed over the diaphragm suspension as the packaging material. The advantage of this temporary packaging technique is twofold. First, it does not substantially increase the size of the PZT thin-film microactuators. Second, it is waterproof thus allowing the microactuators to function in aqueous environments. To evaluate how the temporary package affects the performance of the microactuator, a function generator drives the microactuator at 1, 3, 5, and 10 kHz and a laser vibrometer measures the vibration of the diaphragm suspension before and after the microactuator is packaged. Experimental measurements show that the presence of the package reduces the gain of the microactuator from 0.33 nm/V to 0.15 nm/V. Also, an impedance analyzer measures the impedance of the packaged microactuator, while it is driven in air and in water. The measured impedance shows no difference in air and in water. This indicates that the temporary package is waterproof and the actuator is strong enough to function in an aqueous environment. [ABSTRACT FROM AUTHOR]