Electrostriction of polymer films for microactuators

Abstract

The investigation of electrostrictive polymers (EPs) as a means of microactuation is described. EP materials are squeezed and stretched by electrostatic forces generated with compliant electrodes. This approach offers several advantages over existing actuator technologies, including high strains (> 30%), good actuation pressures (1.9 m a ) , and high specific energy densities (0.1 J/g). In addition, the actuation is fast, uses lightweight materials, and has the potential for high energy efficiencies. Although EP actuators are electrostatics based, they offer 5 to 20 times the effective actuation pressure of conventional air-gap electrostatics at the same electric field strength. The gain is due to replacing air with a higher dielectric material, and to using two orthogonal modes of electromechanical coupling (stretching and squeezing) rather than one. Analysis of the mechanism of EP actuation is discussed. We also discuss fabrication techniques such as spin coating, casting, and dipping, as well as polymer and electrode materials. We describe demonstrations of prototype mini-and microactuators in a variety of configurations such as stretched films, stacks, rolls, tubes, and unimorphs. Last, we suggest potential applications of the technology in areas such as microrobots, sound generators, and displays.

Multi-functional dielectric elastomer artificial muscles for soft and smart machines

“…), where workers applied a stretchable conductor, to the surfaces of soft acrylics and silicone, 13,14 materials with densities approximately the same as natural muscle (and water) but with elastic moduli 10-100 times smaller. 9 It became possible to rapidly and easily apply charge from a source such as a battery in a closely controlled way to the surfaces of a dielectric elastomer, resulting in a shape change, and when the charge was removed, the elastic energy stored in the dielectric returned it to its original shape.…”

“…13,14 The "Maxwell pressure," calculated in Eq. (1) below and experimentally validated by a number of researchers, notably Pelrine, 14 Kofod,16 and Wissler,17 has become the standard interpretation of electromechanical coupling for the DE actuator.…”

On the design of large degree-of-freedom digital mechatronic devices based on bistable dielectric elastomer actuators

“…The development of DE actuators started in the early 1990s [19], [20]. The identification of new and more effective DE materials has made it a very promising actuator technology, with reported laboratory strains of up to 380% [12], [21].…”

On the Kinematics of Parallel Mechanisms with Bi-Stable Polymer Actuators

“…Development of dielectric polymer actuators started in the late 1990s (Pelrine et al, 1997). These actuators are one of a large class of electro active polymers (EAP) that has been studied (Madden et al, 2000).…”

“…An elastomeric film is coated on both sides with compliant electrodes. As a voltage is applied across the electrodes, the electrostatic charges will force the film to compress in thickness and expand in area (Pelrine et al, 1997). This expansion in area can be used to actuate mechanical systems.…”