Investigation of dielectric elastomer actuation for printable mechatronics

The current state of three-dimensional printing technologies enables the fabrication of a wide variety of functional devices. There has been rapid growth in printed electronics; displays, sensors, batteries, and control circuitry have been demonstrated. Commercially available rapid-prototyping systems provide the means to print static three-dimensional mechanical structures. The ability to print fully-functional active electromechanical devices is currently limited by the unavailability of printable actuation. This dissertation presents an investigation into the feasibility of dielectric elastomer actuation for printed mechatronic devices.;This investigation was approached on several fronts. The issue of printability of actuator materials, and design of ancillary components, was addressed using three printing systems: a fused deposition modeler, a 3D inkjet printer, and a pneumatic dispenser printer. A library of flexure-based components was created, and techniques were developed for printing actuator structures and films. Actuator design strategies were discussed, and the characteristics incompatible with printing were presented. Most notable is the requirement of "prestrain," which can improve dielectric elastomer electrical breakdown strength, and thus output performance, over an order of magnitude compared to unstrained films. Birefringence experiments were conducted to analyze the alignment of polymer chains within various prestrained films to determine any correlation to breakdown. It was determined that the minimum birefringence in the plane of the film was a better determining factor than overall maximum birefringence. Finally, several expanding mechanisms were developed as methods to create printable prestrain. Thermally activated expanding microspheres provided a printable internal pressure-generating source for silicone bladders and more advanced contractile elements. Prestrain generating devices demonstrated 30% contraction.;This research has shown that several necessary components to fully functional printed devices are realizable. Hybrid printing techniques offer methods to fabricate more complex mechanical devices than what is achievable with current systems. Initial attempts to characterize the prestrain-breakdown relationship indicate future study of prestrain effects is needed. In particular, the impact of voids on actuator performance should be characterized. With the available set of elastomer materials, it is still possible to create printable prestrain. Bladder and contractile devices presented here provide building blocks for fully printed actuators.