Development and characterization of thinned PZT bulk technology based actuators devoted to a 6-DOF micropositioning platform

Abstract

Piezoelectric actuators are widespread in the design of micro/nanorobotic tools and microsystems, as they have a very interesting electromechanical coupling factor, in addition to their high dynamics and resolution performances. Studies toward the integration of such actuators in complex micromechatronic systems require the size reduction of these actuators while retaining a wide range of performances. Two main fabrication processes are currently used for the fabrication of piezoelectric actuators, providing very different behaviors: (i) the use of a bulk layers and (ii) the use of thin film growth. In this study, we propose to develop micropositioning actuators and platform whose performances are a trade-off between the performances from these two technologies. The proposed trade-off technology allows the development of microsystems with high stiffness, high torque and high dynamics (from technology (i)), as well as, large motion, low voltage and small size (from technology (ii)). Using this technology we designed and fabricated a thick film PZT platform containing eight unimorph beam bending actuators. The Platform allows a high level of performances, both in the static (displacement) and dynamic (first resonance frequency) regimes. The purpose of the fabricated platform is to improve the micromanipulation and microassembly processes, to the point where approaching and manipulating very small object with a high precision will be a very fast and simple operation. These devices were obtained through a room temperature mechanical thinning of a PZT thick layers, after the deposition of Nickel on the bottom side. The piezoelectric beam bending actuators have a 80 μm thick PZT layer on top of a 10 μm thick Nickel layer, a length of 5 mm and a width of 0.5 mm. Experimental characterization has shown that the static displacements obtained are in excess of 1.33 μm/V and the resonance frequencies are up to 1814 Hz, which are very convenient in high dynamics micropositioning applications such as microrobotics and microassembly tasks.