A three-degree-of-freedom thin-film PZT-actuated microactuator with large out-of-plane displacement

Abstract

A novel three degree-of-freedom microactuator based on thin-film lead-zirconate-titanate (PZT) is described with its detailed structural model. Its central rectangular-shaped mirror platform, also referred to as the stage, is actuated by four symmetric PZT bending legs such that each leg provides vertical translation for one corner of the stage. It has been developed to support real-time in vivo vertical cross-sectional imaging with a dual axes confocal endomicroscope for early cancer detection, having large displacements in three axes (z, θx, θy) and a relatively high bandwidth in the z-axis direction. Prototype microactuators closely meet the performance requirements for this application; in the out-of-plane (z-axis) direction, it has shown more than 177 μm of displacement and about 84 Hz of structural natural frequency, when two diagonal legs are actuated at 14V. With all four legs, another prototype of the same design with lighter stage mass has achieved more than 430 μm of out-of-plane displacement at 15V and about 200 Hz of bandwidth. The former design has shown approximately 6.4° and 2.9° of stage tilting about the x-axis and y-axis, respectively, at 14V. This paper also presents a modeling technique that uses experimental data to account for the effects of fabrication uncertainties in residual stress and structural dimensions. The presented model predicts the static motion of the stage within an average absolute error of 14.6 μm, which approaches the desired imaging resolution, 5 μm, and also reasonably anticipates the structural dynamic behavior of the stage. The refined model will support development of a future trajectory tracking controller for the system.

Multi-Photon Vertical Cross-Sectional Imaging With a Dynamically-Balanced Thin-Film PZT z-Axis Microactuator

“…There are various candidate methods for compensating for non-uniformity of actuator motion. One method is through calibration of the actuator model [8] and associated voltage gains at individual legs of an actuator to achieve uniform quasi-static displacements. This approach, however, increases instrument complexity due to additional interconnect requirements to the scanning actuator.…”

“…and Choi et al . [7] [8], achieving up to 500 μ m displacements with bandwidths on the order of 100-200 Hz. Other piezoelectric microactuators with large axial displacements include a thin-film piezoelectric tip-tilt design by Zhu et al [9], though that actuator emphasized rotational scanning angle and thus had more limited scanning depth, and a bulk ceramic actuator with amplified motion by Domke et al [10], though at a larger device size and high voltage.…”

High Bandwidth Microgripper With Integrated Force Sensors and Position Estimation for the Grasp of Multistiffness Microcomponents

“…Extensive researches have been made in the past years on the piezoelectric actuators including their design [10], [32], models [33] and control [34], [35]. Several models have been developed for the piezoelectric actuators in literature [36]- [40].…”

Integrated monolithic 3D MEMS scanner for switchable real time vertical/horizontal cross-sectional imaging

“…An actuator must either move the objective lens [8] or scan out-of-plane [9] to collect vertical images. Several MEMS-based 3D scanners have been developed that can enable tip-tilt-piston motions [6,[10][11][12][13][14], but these devices suffer from coupling between different directions of motion and/or cannot reach as high scanning speeds as current technology. To our knowledge, this is the first report of an integrated, monolithic MEMS scanner that collect images in either the horizontal or vertical plane and can achieve a depth that spans the epithelium of hollow organs.…”

“…Electrothermal devices can provide large axial displacements (>600 µm) at low voltages (∼5 V) but the response time is too slow for in vivo imaging [17]. Piezoelectric scanners in development can achieve large DC displacements, but 3D fast-axis scanning frequencies are limited to date, and fabrication complexity is high [10][11][12]. Electromagnetic scanners have been developed with fast response times and good displacement, but this technology is difficult to scale down in size for most endomicroscopy applications [18].…”