Design, Modeling, and Simulation of a Piezo-MEMS Articulating Arm

Microscale actuators have been a subject of high interest in the past few years, especially for active structural control on the micro and nano scales. This includes manipulation of microparticles, two dimensional RF switching, on-chip electrical probing, and strain sensors. Previous developments for micro-actuators exhibit deflection in the vertical direction (both positive and negative). This paper presents a novel design for a cantilever piezoelectric microactuator. The design proposed is capable of actuation in the vertical as well as the horizontal direction by having a trapezoidal cross-section. This cross-section allows for the deposition of electrodes (platinum) onto sloped sidewalls, resulting in added degrees of freedom. The actuators are fabricated from link sections of traditional piezoelectric materials such as lead titanate zirconate (PZT). Currently, only single link actuators have been investigated. For the double link actuator, two sections will be connected by a joint consisting of silicon nitride, allowing for the independent actuation in the X, Y, and Z axes of each section for each specific cantilever beam. Through the utilization of voltage as the drive for the actuation, it is possible to counteract lingering oscillations in the beam resulting from initial motion. Control for this microactuator is comparable to rigid robotic structures, taking into account the modeled behavior of piezoelectric materials as well as the bending model of a trapezoidal cantilever beam. The research and development for this paper will include design, as well as dynamic modeling and simulation of a piezo-MEMS robot arm. Fabrication consists of a series of spin-casting and annealing steps to create the piezoelectric films, the polarity of which is determined by a poling process subsequent to fabrication. Conducting materials are deposited both before the PZT (bottom electrode) and after (top and sidewall electrodes), while their thicknesses will be minimalized in order to not adversely affect the beam stiffness of the piezoelectric links.