Gold Layers on Elastomers near the Critical Stress Regime

Soft electrodes are essential components of soft robotics, tunable optics, microfluidics, flexible electronics, neuroprosthetics, and dielectric elastomeric transducers (DET). The two main paths employed to increase an electrode's compliance involve the manipulation of either its intrinsic material properties or its structural features, such as the introduction of wrinkles, which arise above the critical stress of metal films on elastomeric substrates. Herein, this study demonstrates that the interplay between functionalized oxygen‐plasma‐treated polydimethylsiloxane (PDMS) films and sputter‐deposited metal electrodes allows for conserving compressive stress within the electrode. Insulator–metal transition already occurs for 10 nm thin Au electrodes, and below this electrode thickness, atomic force microscopy nanoindentations with sub‐micrometer resolutions reveal no stiffening of the Au/PDMS heterostructure. These DETs exhibit reduced electrocreasing, which is a significant contributor to structural failure, while their enhanced dielectric breakdown field of up to 120 V µm–1 enables calculated strains above 10% — a crucial requirement for thin‐film DETs such as those used for artificial muscles. The interplay between functionalized oxygen‐plasma‐treated polydimethylsiloxane (PDMS) films and sputter‐deposited Au electrodes enables the conservation of compressive stress on the top layer. Its mechanical compliance is increased through structural features, such as the introduction of wrinkles by oxygen‐plasma treatment. Atomic force microscopy nanoindentations with sub‐micrometer mapping reveal anisotropies in the elastic modulus for the plasma‐treated PDMS films.