The research objective of this award is to integrate polymer and piezoelectric micro-structures to create robust, sub-centimeter terrestrial micro-robots, and to use a combination of modeling and experimentation to evaluate leg dynamics of such robots. Specifically, high-aspect ratio parylene flexural mechanisms will be integrated with thin-film lead-zirconate-titanate (PZT) actuators in complex, multi-degree-of-freedom micro-robotic leg joints. Experimental measurements of parylene structure response to integrated thin-film PZT actuation or external bulk PZT ceramic or load cell actuation will be used to characterize parylene stiffness and damping characteristics at varying strain rates, relative to high-strain rate piezoelectric actuation. Adhesion between bulk-micromachined silicon trench surfaces and PZT/metal stack layers will also be evaluated. Measured parylene properties will then be incorporated into existing micro-robotic foot-terrain models developed by the PI and students to produce simulation models of PZT-polymer robots that can be validated against experimental robot prototypes.

Successful completion of this work would dramatically improve the ability of walking millimeter-scale micro-robots to move over uneven terrain, thus increasing the range of possible interactions between human operators and engineered or natural systems. The target user community for millimeter-scale autonomous robots includes disaster response teams, infrastructure maintenance and monitoring workers, and national security organizations. The framework to be deployed would be a technique to embed piezoelectric microactuators in resilient micro-robotic appendages, producing sample walking micro-robot platforms. Results from this research would be coupled into both undergraduate and graduate curriculum and secondary school education. The latter effort will consist of interactive hands-on and web-based projects developed by the PI for use in science education for the local Ypsilanti, Michigan school district and the broader community of interested citizens.

Project Report

The goal of this project was to develop a new leg technology for sub-centimeter scale micro-robots. The legs would use piezoelectric materials, which contract under an applied electric voltage, to act as muscles, attached to mechanisms formed from thin polymer beams, which would permit conversion of piezoelectric force into motion in various directions. The properties of the piezoelectric and polymer materials would be characterized for non-linear properties relevant to dynamic modeling of robot gaits. A variety of simple actuation test structures and more complex robot prototypes were successfully fabricated on silicon wafers. Actuators and robots were tested in both static and dynamic motion, with results compared to prior studies of material properties and to mathematical models for integrated piezoelectric and polymer behavior, developed in part by the investigators. Static and low voltage material properties were found to be in agreement with established results from the literature, while efforts to identify changes to properties in high voltage and high speed operation were inconclusive, but will continue beyond the conclusion of the award. Micro-robots prototypes were manufactured based on insect-inspired hexapod and millipede architectures. Simple hexapod robots with dimensions of 5 mm x 3 mm x 100 µm achieved multiple-leg motion in forward and vertical axes, while supported inside the silicon chip in which they were produced. More complex robots with dimensions of approximately 10 mm x 6 mm x 100 µm were extracted from the silicon wafer. The polymer leg mechanisms were found to have superior structural robustness to prior silicon-based leg designs, though further improvement of electrical properties are required for testing of tethered and/or autonomous operation. Dynamic behavior of the robots was found to agree closely with mathematical models. In addition to primary research activities, the award supported mentoring of one post-doctoral fellow and two undergraduate research assistants at the University of Michigan, and microfabrication facility support for a Graduate Research Assistant. Sample robot technologies from the project were used in dissemination of results to the broader local community at Michigan Robotics Day, in Ann Arbor, MI, and an engineering outreach unit to Ypsilanti Middle School, Ypsilanti, MI. Robot leg structures from this research were also used as examples of dynamic systems in undergraduate laboratory and graduate control systems courses.

Project Start
Project End
Budget Start
2012-09-01
Budget End
2014-08-31
Support Year
Fiscal Year
2012
Total Cost
$195,195
Indirect Cost
Name
Regents of the University of Michigan - Ann Arbor
Department
Type
DUNS #
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109