Electrodes For Dielectric Elastomer Actuators Research Articles

In silico optimization of aligned fiber electrodes for dielectric elastomer actuators

Dielectric elastomer actuators (DEAs) exhibit fast actuation and high efficiencies, enabling applications in optics, wearable haptics, and insect-scale robotics. However, the non-uniformity and high sheet resistance of traditional soft electrodes based on nanomaterials limit the performance and operating frequency of the devices. In this work, we computationally investigate electrodes composed of arrays of stiff fiber electrodes. Aligning the fibers along one direction creates an electrode layer that exhibits zero stiffness in one direction and is predicted to possess high and uniform sheet resistance. A comprehensive parameter study of the fiber density and dielectric thickness reveals that the fiber density primary determines the electric field localization while the dielectric thickness primarily determines the unit cell stiffness. These trends identify an optimal condition for the actuation performance of the aligned electrode DEAs. This work demonstrates that deterministically designed electrodes composed of stiff materials could provide a new paradigm with the potential to surpass the performance of traditional soft planar electrodes.

Conductive stretchable composites properly engineered to develop highly compliant electrodes for dielectric elastomer actuators

Carbon black (CB) particles were used as conductive filler for a high molecular weight polydimethylsiloxane-α,ω-diol (PDMS) to obtain conductive stretchable electrodes suitable for dielectric elastomer actuators. To ensure a perfect compliance between electrodes and the dielectric film, both based on the same PDMS, an original procedure consisting in their co-crosslinking was approached. Some of the Si–OH groups from the electrode solution will condensate with residual Si–OH groups from the surface of the dielectric elastomer (DE) creating chemical bridges. Electrode morphologies were examined by scanning electron microscopy, while their conductivities were evaluated by four-point method. Also, the electrodes influence on mechanical, viscoelastic and actuation properties on the resulted actuators was studied. Good results were obtained consisting in that the chemically bonded electrodes support large deformations (200%) without losing conductivity even after 10 000 cycles with no significant impact on the DE stiffness. The DE transducers exhibit electromechanical actuation of approximately 81% greater than that achieved with the same dielectric but with electrodes consisting of loose CB nanoparticles.

Low-voltage dielectric elastomer actuators with stretchable electrodes fabricated by supersonic cluster beam implantation

Supersonic cluster beam implantation of Ag nanoparticles is proposed for the fabrication of stretchable and compliant electrodes for dielectric elastomer actuators (DEAs) with reduced thickness. Thanks to the low-energy and finely tunable implantation process, a nanocomposite Ag/polydimethylsiloxane electrode layer is produced with a moderate stiffening effect for the DEA in contrast with a common deposition strategy for electrodes. Thin DEAs with an overall thickness of 17 μm were fabricated and tested under different preloading conditions, demonstrating a max uniaxial actuation strain of 2.5% at an actuation voltage of 765 V, lower than the typical voltage values of DEAs. The electrodes remained conductive up to 40% strain, and they fully recovered the original resistance after 70% stretching. Our results represent a significant step towards the development of DEAs operating at reduced actuation voltages, by stacking of micrometer-thick elastomer films, paving the way to novel applications in soft robotics.

Stretchable composite monolayer electrodes for low voltage dielectric elastomer actuators

In this work, a Multiwalled Carbon Nanotube/poly(alkylthiophene) (MWCNT/PT) composite is developed as the electrodes for dielectric elastomer actuators (DEAs) using the Langmuir-Schaefer (LS) method. These composites form stable monolayers at the air-water interface that can then be LS transferred onto a poly(dimethylsiloxane) (PDMS) elastomer membrane. The monolayer electrode remains conductive up to 100% uniaxial strain. We present a method to fabricate DEAs using the LS transferred electrodes. By using a mask during the transfer step, the electrodes can be patterned with better than 200 μm resolution on both sides of a 1.4 μm-thick pre-stretched PDMS membrane to produce an ultra-low voltage DEA. The DEA generates 4.0% linear strain at an actuation voltage of 100 V, an order of magnitude lower than the typical DEA operating voltage.

Dielectric elastomer unimorph using flexible electrodes of electrolessly deposited (ELD) silver

Abstract This paper demonstrated electroless deposition of silver thin film on a substrate of elastomeric VHB tape (both VHB 9469PC and 9473PC tapes). ELD silver forms a conformable and clean electrode with uniform thickness on the tape. Experiments showed that the silvered electrode on the tape remains conductive when it is stretched up to a uniaxial strain of 10%. Resistance increases with the strain. Crack lines are formed permanently to the electrode, which is stretched at and above a 4% strain. As a result, a hysteresis is observed from the path of resistance versus strain when the electrode is stretched and relaxed in cycles below a 10% strain. Nevertheless, this ELD silver coating makes flexible electrodes for dielectric elastomer actuators (DEA). A dielectric elastomeric unimorph is developed based on these ELD silvered VHB tapes and a passive layer of silicone rubber. This elastomeric unimorph is demonstrated with a large bending as much as 74° at 4 kV. It can operated repeatedly and reversibly below the breakdown voltage. This unimorph is measured to undergo a longitudinal actuation strain of up to 2.5% at 4 kV. This measured strain lies between the theoretical bounds. Theoretical analysis shows that the thin-film silver electrodes are flexible, with negligible flexural stiffness, and they do not restrict bending of the DEA.