Andreas Tröls

Stretch dependence of the electrical breakdown strength and dielectric constant of dielectric elastomers

Dielectric elastomers are used for electromechanical energy conversion in actuators and in harvesting mechanical energy from renewable sources. The electrical breakdown strength determines the limit of a dielectric elastomer for its use in actuators and energy harvesters. We report two experimental configurations for the measurement of the stretch dependence of the electrical breakdown strength of dielectric elastomers, and compare the electrical breakdown fields for compliant and rigid electrodes on the elastomer. We show that the electrode configuration strongly influences the electrical breakdown field strength. Further, we compare the stretch dependent dielectric function and breakdown of the acrylic elastomer VHB 4910 TM from 3M TM , and of the natural rubber ZruElast TM A1040 TM from Zrunek rubber technology. While the dielectric permittivity of VHB decreases with increasing stretch ratio, the dielectric constant of rubber is insensitive to stretch. Our results suggest natural rubber as a versatile material for dielectric elastomer energy harvesting. (Some figures may appear in colour only in the online journal)

Natural rubber for sustainable high-power electrical energy generation

Clean, renewable and abundant sources of energy, such as the vast energy of ocean waves, are untapped today, because no technology exists to convert such mechanical motions to electricity economically. Other sources of mechanical energy, such as motions of people and vibrations of buildings and bridges, can potentially power portable electronics and distributed sensors. Here we show that natural rubber can be used to construct generators of high performance and low cost. Natural rubber has higher elastic modulus, fracture energy and dielectric strength than a commonly studied acrylic elastomer. We demonstrate high energy densities (369 mJ g−1) and high power densities (200 mW g−1), and estimate low levelized cost of electricity (5–11 ct kW−1 h−1). Soft generators based on natural rubber enable clean, low-cost, large-scale generation of electricity.

Modeling and fabrication of low-cost electrowetting actuators for flexible microfluidic display applications

We investigate and characterize three different fabrication methods facilitating low-cost electrowetting on dielectric (EWOD) structures. EWOD allows setting fluid droplets in motion by electrically altering the surface tension equilibrium at the triple contact line. We present a fabrication method for flexible EWOD structures by screen printing a transparent and conducting poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate (PDOT:PSS) polymer on polyethylene terephthalate (PET) foil. As a demonstator for applications, a prototype of a flexible microfluidic EWOD display cell is FEM simulated and characterized in terms of feasibility and response speed for various pixel scalings. The accordingly constructed microfluidic pixel serves as a basis cell for a future flexible EWOD cell multigrid where all pixels are directly addressable.

FEM-Simulation and Experimental Realization of Low-Cost Electrowetting Actuators for a Flexible Microfluidic Pixel

We investigate and characterize three different fabrication methods facilitating low-cost electrowetting-on-dielectric (EWOD) structures. EWOD allows setting fluid droplets in motion by electrically altering the surface tension equilibrium at the triple contact line. We present a fabrication method for flexible EWOD structures by screen printing a transparent and conducting poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate (PDOT:PSS) polymer on polyethylene terephthalate (PET) foil. As a demonstrator for applications, i.e., a flexible microfluidic EWOD display cell is simulated using FEM and characterized in terms of feasibility and response speed for various pixel scaling. The accordingly fabricated microfluidic pixel serves as a basis cell for a bendable and flexible EWOD cell multigrid, where all pixels are directly addressable.