Metal Ion Implantation for the Fabrication of Stretchable Electrodes on Elastomers

We report on low-energy metal ion implantation by filtered cathodic vacuum arc to create highly deformable electrodes on polydimethylsiloxane (PDMS) membranes. Implantation leads to the creation of nanometer-size clusters in the first 50 nm below the surface. When the elastomer is stretched, these small clusters can move relative to one another, maintaining electrical conduction at strains of up to 175%. Sheet resistance vs. ion dose, resistance vs. strain, time stability of the resistance, as well as the impact of implantation on the elastomer’s Young’s modulus are investigated for gold, palladium and titanium implantations. Of the three tested metals, gold has the best performance, combining low and stable surface resistance (0.1 − 10 kOhm/square, unchanged after 8 months), very high strain capabilities before loss of electrical conduction (up to 175%), as well as low impact on the Young’s modulus of the PDMS membrane (+50%). These electrodes have been cyclically strained to 30% for more than 105 cycles and remain conductive. In contrast sputtered or evaporate metals films cease to conduct at strains of order 3%. Additionally, metal ion implantation allows creating electrodes that are semi-transparent. The optical transmission through 25 μm-thick PDMS membranes decreases from 90% to 60% for Pd-implantations at doses used to make stretchable electrodes. The implantation technique presented here allows the rapid production of reliable stretchable electrodes for a number of applications including dielectric elastomer actuators as well as foldable or rollable electronics.