Multi-Degree-of-Freedom Thin-Film PZT-Actuated Microrobotic Leg

Abstract

As a novel approach to future microrobotic locomotion, a multi-degree-of-freedom (m-DoF) microrobotic appendage is presented that generates large range of motion (5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> -40 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> ) in multiple axes using thin-film lead zirconate titanate (PZT) actuators. Due to the high driving force of PZT thin films and a robust fabrication process, m-DoF legs that retain acceptable payload capacity ( ~ 2 mg per leg) are achieved. The fabrication process permits thin-film PZT actuator integration with more complex higher aspect ratio silicon structures than previous related processes, using vertical silicon dioxide barrier trenches formed before PZT deposition to provide robust encapsulation of the silicon during later XeF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> release. Planarization of the barrier trenches avoids detrimental effects on piezoelectric performance from the substrate alteration. Once fabricated, kinematic modeling of compact PZT actuator arrays in prototype leg joints is compared to experimental displacement measurements, demonstrating that piezoelectric actuator and assembled robot leg joint performance can be accurately predicted given certain knowledge of PZT properties and residual stress. Resonant frequencies, associated weight bearing, and power consumption are also obtained.