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

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.