While Electroactive Polymer Artificial Muscle (EPAM) has been presented extensively as a solution for actuation and generation technology, EPAM technology can also be used in multiple novel applications as a discrete or integrated sensor. When an EPAM device, an elastic polymer with compliant electrodes, is mechanically deformed, both the capacitance of the EPAM device, as well as the electrode and dielectric resistance, is changed. The capacitance and resistance of the sensor can be measured using various types of circuitry, some of which are presented in this paper. EPAM sensors offer several potential advantages over traditional sensors including operation over large strain ranges, ease of patterning for distinctive sensing capabilities, flexibility to allow unique integration into components, stable performance over a wide temperature range and low power consumption. Some existing challenges facing the commercialization of EPAM sensors are presented, along with solutions describing how those challenges are likely to be overcome. The paper describes several applications for EPAM sensors, such as an integrated diagnostic tool for industrial equipment and sensors for process and systems monitoring.
Electroactive Polymer Artificial Muscle (EPAM[R]) technology is becoming a robust, high performance, cost effective solution for commercial applications in many sectors. Since its inception in 2004, Artificial Muscle, Inc. (AMI), a spinout company from SRI International, has rigorously pursued the commercialization of this form of artificial muscle technology through innovative designs and fabrication processes, dramatically increasing performance, reliability and manufacturability across a wide variety of applications. Scaleable solutions developed by AMI include air and liquid pumps, valves, linear and angular positioners, rotary motors, sensors and generators. Innovative device designs demonstrating the ability to meet the specifications of demanding applications across broad operating environments and combining practical levels of power densities and actuation lifetimes will be discussed. Integrated electronics control modules allow the freedom to design artificial muscles directly into new or existing product lines while effectively managing the transition from conventional technologies. Simple modular, versatile designs, coupled with low cost industrial materials and flexible automated manufacturing processes, provide a cost effective solution for products serving such diverse industries as consumer electronics, medical devices, and automobiles. Several case examples are presented to illustrate the commercial viability of EPAM[R]-based devices.
Many different actuator configurations based on SRI International’s dielectric elastomer (DE) type of electroactive polymer (EAP) have been developed for a variety of applications. These actuators have shown excellent actuation properties including maximum actuation strains of up to 380% and energy densities of up to 3.4 J/g, using the planar mode of actuation. Recently, SRI has investigated different configurations of DE actuators that allow complex changes in surface shape and thus the creation of active surface texture. In this configuration, the “active” polymer film is bonded or coated with a thicker passive layer, such that changes in the polymer thickness during actuation of the DE device are at least partially transferred to (and often amplified by) the passive layer. Although the device gives out-of-plane motion, it can nonetheless be fabricated using two-dimensional patterning. The result is a rugged, flexible, and conformal skin that can be spatially actuated by subjecting patterned electrodes on a polymer substrate to an electric field. Using thickness-mode DE, we have demonstrated thickness changes of the order of 0.5 - 2 mm by laminating a passive
elastomeric layer to a DE polymer that is only 60 μm in thickness. Such thickness changes would otherwise require a very large number of stacked layers of the DE film to produce comparable surface deformations. Preliminary pressures of 4.2 kPa (0.6 psi) in a direction normal to the plane of the DE film have been measured. However, theoretical calculations indicate that pressures of the order of 100 kPa are feasible using a single layer of DE film. Stacking multiple layers of DE film can lead to a further increase in achievable actuation pressures. Even with current levels of thickness change and actuation pressures, potential applications of such surface texture change are numerous. A thin, compliant pad made from these actuators can have a massaging or sensory augmentation
function, and can be incorporated into garments if desired. The bumps and troughs could act as valves or pumping elements in a fluidic or microfluidic system. Such a device could also be the basis of a smart skin that controls boundary-layer flow properties in a boat or airplane so as to reduce overall drag. The DE elements of the pad can also be used as sensors to make a touch-sensitive skin for recording human interaction with the environment. By driving a thin, compliant vibrating layer at resonant frequencies, one can also configure these devices as solid or fluidic conveyors that transport material on a macroscopic or microscopic scale.