Thin-film piezoelectric and high-aspect ratio polymer leg mechanisms for millimeter-scale robotics

Abstract

Millimeter-scale micro-robotic leg actuators are described that integrate thin-film lead zirconate titanate (PZT) piezoelectric actuation with compliant structures formed from parylene-C polymer. Models for out-of-plane rotation using piezoelectric cantilevers and in-plane rotation using highaspect ratio polymer beams are discussed. Opportunities are highlighted for thin polymer films to aid in load-bearing, flexibility, and resilience of piezoelectric micro-robot appendages. A simple 5 mm 9 2.4 mm 9 0.15 mm hexapod robot prototype incorporating multiple actuators in each leg assembly is fabricated and tested within the silicon wafer in which it was built. Completed robot leg performance shows close agreement between modeled and tested static and dynamic characteristics, with potential benefits for future walking micro-robots from low power requirements relative to payload capacity and large amplitude motion at resonance.

Dynamic Structural and Contact Modeling for a Silicon Hexapod Microrobot

“…As a candidate autonomous walking robot technology, comparison of the current robot's range of motion has been done in Ref. [19], with a basic projection of velocity, though findings from this work would suggest a reduction in robot speed and payload capacity due to squeeze-film damping and adhesion.…”

“…Details on robot actuator design, fabrication, and testing have been presented in Refs. [8] and [19]. In brief, the robot consists of a central silicon chassis or body (30 lm thick silicon), surrounded by six nominally identical legs.…”

“…With nominal robot design parameters and fabrication results as reported in Ref. [19], the first lateral resonant frequency of the hip actuators is simulated to be 498 Hz; the first vertical frequency of knee actuators is 3671 Hz. Figure 3 shows the simulated structural deformation of these first two modes of the robot legs.…”

Elastically and Plastically Foldable Electrothermal Micro‐Origami for Controllable and Rapid Shape Morphing

“…We select the large-displacement microgripper as our target because it is difficult to create this type of mechanisms with a traditional microfabrication process at smaller scales. [34,36] With traditional MEMS-based methods, out-of-plane motions for gripping can be achieved with different actuator systems. [29][30][31][32][33][34] However, existing systems usually have folding angles of less than 90°, and have been difficult to integrate into origami designs with more complex motions and functions.…”

“…Although microscale origami is a relatively young field of research, there has been related work on creating actuators for micro-electromechanical systems (MEMS) that provides helpful insight on how to implement active systems at small scales. Piezoelectric-material-based actuators, electrothermal actuators, and electrostatic actuators are capable of achieving out-of-plane motions, [29][30][31][32][33][34] and the electrothermal actuators show potential for generating relatively large folding angles. [35] However, most of these currently available electrothermal actuator designs are not capable of folding beyond 90° from the initial flat state, which limits their usage for application in micro-origami systems where complex shapes with large folding are desired.…”