Nanomechanical Probing of Thin-Film Dielectric Elastomer Transducers
Journal Article - Open Access
Biomaterials Science Center, Department of Biomedical Engineering, University of Basel Allschwil Switzerland
Pagination or Media Count:
Dielectric elastomer transducers DETs have attracted interest as generators, actuators, sensors, and even as self-sensing actuators for applications in medicine, soft robotics, and microfluidics. Their performance crucially depends on the elastic properties of the electrode-elastomer sandwich structure. The compressive displacement of a single-layer DET can be easily measured using atomic force microscopy AFM in the contact mode. While polymers used as dielectric elastomers are known to exhibit significant mechanical stiffening for large strains, their mechanical properties when subjected to voltages are not well understood. To examine this effect, we measured the depths of 400 nanoindentations as a function of the applied electric field using a spherical AFM probe with a radius of 52264 nm. Employing a field as low as 20 Vlm, the indentation depths increased by 42 at a load of 100 nN with respect to the field-free condition, implying an electromechanically driven elastic softening of the DET. This at-a-glance surprising experimental result agrees with related nonlinear, dynamic finite element model simulations. Furthermore, the pull-off forces rose from 23.060.4 to 49.060.7 nN implying a nanoindentation imprint after unloading. This embossing effect is explained by the remaining charges at the indentation site. The root mean-square roughness of the Au electrode raised by 11 upon increasing the field from zero to12 Vlm, demonstrating that the electrodes morphology change is an undervalued factor in the fabrication of DET structures.
- Electrical and Electronic Equipment