Towards fast, reliable, and manufacturable DEAs: miniaturized motor and Rupert the rolling robot

Abstract

Dielectric elastomer transducers (DETs) are known for their large strains, low mass and high compliance, making them very attractive for a broad range of applications, from soft robotics to tuneable optics, or energy harvesting. However, 15 years after the first major paper in the field, commercial applications of the technology are still scarce, owing to high driving voltages, short lifetimes, slow response speed, viscoelastic drift, and no optimal solution for the compliant electrodes. At the EPFL's Microsystems for Space Technologies laboratory, we have been working on the miniaturization and manufacturability of DETs for the past 10 years. In the frame of this talk, we present our fabrication processes for high quality thin-film silicone membranes, and for patterning compliant electrodes on the sub mm-scale. We use either implantation of gold nano-clusters through a mask, or pad-printing of conductive rubber to precisely shape the electrodes on the dielectric membrane. Our electrodes are compliant, time stable and present strong adhesion to the membrane. The combination of low mechanicalloss elastomers with robust and precisely-defined electrodes allows for the fabrication of very fast actuators that exhibit a long lifetime. We present di↵erent applications of our DET fabrication process, such as a soft tuneable lens with a settling time smaller than 175 microseconds, a motor spinning at 1500 rpm, and a self-commutating rolling robot.

Fabrication Process of Silicone-based Dielectric Elastomer Actuators

“…Unlike the widely used carbon grease or loose powder electrodes applied manually, our approach leads to precisely defined electrodes that present a strong adhesion to the membrane on which they are applied. They are very resistant to wear, and cannot be delaminated from the membrane 13 . Despite the fact that pad printing is a contact method, it can be used to apply ink on thin and fragile silicone membranes, because the only part coming in contact with the membrane is a soft silicone stamp.…”

“…In this process, ink is applied with a doctor blade on a cliché (a steel plate on which the design to be printed is etched, and subsequently picked up from the cliché by a smooth silicone stamp before being transferred to the membrane 13 ). Every design requires its own cliché.…”

“…A self-commutating rolling robot was built to run laps along a circular track (Figure 10C). The robot travelled more than 25 km at an average speed of 15 cm/sec 13 .…”

“…This is for example demonstrated through the fabrication of a DEA-based rotary motor comprising three electrically independent electrodes ( Figure 10B). The axis and proof mass at the center of the motor can spin at 1,500 rpm 13 . The motor concept has been pushed further to show that pad printing can also produce reliable actuators.…”

Small, fast, and tough: Shrinking down integrated elastomer transducers

“…In this prospect, it is important to have electrodes that are solid and that present a good adhesion to the membrane in order to prevent mechanical abrasion. Suitable electrodes include conductive rubber made by dispersing conductive particles (such as carbon black) into an elastomer 75,103,104 , or soft ionic gels 105,106 . Multilayer actuators can use electrodes made of loose particles, as the electrode will be encapsulated by the next dielectric layer (see e.g.…”