Ronald E. Pelrine

Electrostriction of polymer dielectrics with compliant electrodes as a means of actuation

Abstract The electrostriction of elastomeric polymer dielectrics with compliant electrodes is potentially useful as a small-scale, solid-state actuator technology. Electrostrictive polymer (EP) materials are capable of efficient and fast response with high strains (> 30%), good actuation pressures (up to 1.9 MPa), and high specific energy densities (up to 0.1 J g−1). In this article, the mechanism of electrostriction is shown to be due to the electrostatic attraction of free charges on the electrodes. Although EP actuators are electrostatics based, they are shown to produce 5–20 times the effective actuation pressure of conventional air-gap electrostatics at the same electric field strength. The thin uniform dielectric films necessary for fabrication of EP actuators have been fabricated by techniques such as spin coating, casting, and dipping. A variety of materials and techniques have been used to produce the compliant electrodes, including lift-off stenciling techniques for powdered graphite, selective wetting of ionically conductive polymers, and spray coating of carbon blacks and fibrils in polymeric binders. Prototype actuators have been demonstrated in a variety of configurations such as stretched films, stacks, rolls, tubes, and unimorphs. Potential applications of the technology in areas such as microrobots, sound generators, and displays are discussed in this article.

Incremental Inspection for Microrobotic Quality Assurance

This paper addresses inspection techniques that can be performed by microrobots used for fabricating three dimensional structures. In contrast to most commercial rapid prototyping processes, the parallelism afforded by microrobot teams allows incremental inspection of structures during assembly. In the present case, this approach is applied to parts fabricated from carbon fiber struts bonded with UV-cured epoxy. Preliminary tests involving thermal and vibrational inspection methods are described and compared with the results of FEA models of the joints. Vibrational inspection performed by microrobots and recorded using a directional microphone, characterizes bond joint natural frequency with good resolution (an average measurement standard deviation of 5Hz over a range of 650–1215 Hz). These effective stiffness measurements are correlated with ultimate bond strength as well. The measurements are sufficient to distinguish between joints that do or do not have desired amounts of adhesive.Copyright

5-kV switches on flexible plastic substrate for electro-active polymer actuators

In this paper, we demonstrate high voltage (up to 5-kV) thin film switches made on Kapton foil and their integration into a nine-element EAP actuator array. The DC high voltage is supplied to each actuator through a photoconductive switch, which is addressed with a laser. Each cell of the array consists of a 1-cm/sup 2//spl times/30-/spl mu/m thick acrylic diaphragm and a 310-nm thick amorphous silicon switch.