Nanomechanical probing of thin-film dielectric elastomer transducers

Abstract

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 (522 ± 4) nm. Employing a field as low as 20 V/μm, 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 (23.0 ± 0.4) to (49.0 ± 0.7) 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 to 12 V/μm, demonstrating that the electrode's morphology change is an undervalued factor in the fabrication of DET structures.

Siloxane Matrix Molecular Weight Influences the Properties of Nanocomposites Based on Metal Complexes and Dielectric Elastomer

“…Silicones have the disadvantages of low permittivity [ 9 ], and this leads to the increased activation voltages required for reasonable actuation effects. The literature presents the use of multiple types of fillers capable of improving the permittivity of dielectric polymer materials by using one of the following materials: ceramic particles such as titanium dioxide, barium titanate, magnesium niobate; [ 10 , 11 , 12 , 13 , 14 ], conductive particles such as carbon allotropes, metal complexes and copper-phthalocyanine/polyaniline [ 15 , 16 ]; and conjugated polymers such as poly(3-hexyltiophene), polyaniline, polythiophene [ 17 ], that can be introduced in the siloxane matrix by blending or as nanoparticles [ 11 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ].…”

Conducting and stretchable nanometer-thin gold/thiol-functionalized polydimethylsiloxane films

“…The obtained adhesion forces related to the contact area of the indenter, given by its radius. 31 Therefore, the peak with the highest adhesion force is associated with the groove-like depressions, whereas the peak with the lowest adhesion force corresponds to the protrusions of the wrinkled surface.…”

Deep Insight into the Influences of the Intrinsic Properties of Dielectric Elastomer on the Energy-Harvesting Performance of the Dielectric Elastomer Generator

“…The dielectric elastomer transducer (DET) has been a hot area of research in recent decades due to its high flexibility, light weight, large mechanical strain, simple structure and low cost [ 1 , 2 , 3 , 4 ]. A typical DET device consists of a dielectric elastomer (DE) film sandwiched by two compliant electrodes [ 5 , 6 ].…”