The Röntgen Experiment - A Historical Idea Opening up Interesting Possibilities for Dielectric Elastomer Actuator Design and Material Characterization
Sprache des Vortragstitels:
2009 MRS Spring Meeting, San Francisco, USA
Sprache des Tagungstitel:
Dielectric elastomer actuators (DEAs) are emerging as one of the most promising technologies for polymer-based electromechanical transduction in the last few years. Interestingly the first description of the physical mechanism underlying the working principle of DEAs was already given by Röntgen in 1880. In an experiment he used sprayed-on electrostatic charges originating from corona discharges to deform a prestretched stripe of natural rubber. Modern DEA setups consist of synthetic elastomer films sandwiched between compliant electrodes which are connected to a driving voltage. Here we want to reason how modern DEA research could benefit from Röntgen’s idea and we show examples of actuators operated with sprayed-on charges, where a linear actuator, similar to the historic setup used by Röntgen, is instructively modeled. Both the historical and the contemporary approach lead to a deformation of the elastomer, although the way of providing electrical energy to the system differs. Connecting electrodes to a voltage source results in a voltage controlled actuator system, whereas Röntgen’s method has to be considered as a charge controlled DEA. A major difference in the physical description of these systems arises, since the capacitance dependence of the DEA’s free energy strongly differs in both cases. So the deformation behavior is influenced by the method chosen to supply the system with electrical energy. Moreover, compliant electrodes form an equipotential surface whereas sprayed-on charges have to be treated as a fixed but spatially varying surface charge density allowing for sophisticated applications with tunable surface charge inhomogeneities. Spraying-on charges opens up electrode free design alternatives for dielectric elastomer actuators, but what is maybe of even greater interest are the benefits of this technique for material characterization such as dielectric and material strength tests.