Though the field of dielectric elastomer transducers has been around for several years, the vast majority of devices that appear in the literature on based on high loss acrylic elastomer and manually applied carbon (typically grease) electrodes. Though sufficient for quick demonstration and the macro scale, devices made using these methods typically possess low reproducibility and lack mechanical robustness. Moreover these methods and inadequate when attempting to fabricate transducers on a micro scale e.g. for producing micro-actuators for mechanical stimulation of biological cells.
High-resolution, large-area patterning of compliant silicone-carbon electrodes for dielectric elastomer transducers
We have developed a novel technique for the production of high-resolution compliant electrodes on silicone dielectric elastomer transducers. The method consists in casting compliant electrodes onto water-soluble sacrificial substrates (polyvinyl alcohol or PVA), and then patterning the electrode by laser ablation. The patterned electrodes are then transferred to a silicone membrane using oxygen plasma activation. The electrode substrate is subsequently removed by dissolving in hot water. The general fabrication process is summarized in the figure below.
Patterning by laser ablation provides the possibility for making intricate and high-resolution shapes (feature size < 100 µm demonstrated), as shown below (left). Casting the electrode layer enables large-area electrodes to be produced enabling the fabrication of large area arrays of devices (shown below right).
The use of bonding by oxygen plasma treatment provides excellent electrode adhesion to the elastomer membrane, resulting in highly mechanically robust devices resistant to large mechanical deformations (as demonstrated in the image below left).
We have use this technique to fabricate highly sensitive and highly conformal interdigitated capacitive touch sensors (see image above right), which function even when highly deformed as shown in the figure below.
The power of our fabrication technique is further demonstrated in the video below showing a highly integrated actuator-sensor device. The device has a dielectric elastomer actuator in the shape of the word “PLAY”, where the letter “A” has been replaced by an interdigitated capacitive sensor similar to the capacitive sensor mentioned above (a schematic cross section of the device is shown below). As can be seen from the video, the sensor responds only to touches made in the sensor region (the “A”) and not to touches made in the surrounding membrane. This demonstrator opens the door to the development highly complex and responsive DETs using our technique.
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Development and performance evaluation of a high mass resolution time of flight laser ablation ionisation mass spectrometer
Chemical and Optical Identification of Micrometer-Sized 1.9 Billion-Year-Old Fossils by Combining a Miniature Laser Ablation Ionization Mass Spectrometry System with an Optical Microscope
2015.TRANSDUCERS 2015 – 2015 18th International Solid-State Sensors, Actuators and Microsystems Conference, Anchorage, AK, USA, 21-25 June 2015. p. 1905-1908. DOI : 10.1109/TRANSDUCERS.2015.7181323.
(Repsonse of interdigitated capacitive sensors to high-permittivity insulators and grounded conductors as a function of distance away from sensor surface. The capacitance of the sensor changes in relation to the permittivity of the objects in its immediate vicinity, increasing when high permittivity insulators are close, or decreasing for grounded conductors. Adapted with permission from: O. A. Araromi, S. Rosset, and H. Shea, “High-resolution, large-area fabrication of compliant electrodes via laser ablation for robust, stretchable dielectric elastomer actuators and sensors,” ACS Appl. Mater. Interfaces, 2015. © 2015 American Chemical Society)