Dielectric elastomer-based energy harvesting: Material, generator design, and optimization

Electroactive polymers are soft capacitors made of thin elastic and electrically insulating films coated with compliant electrodes offering a large amount of deformation. They can either be used as actuators by applying an electric charge or used as energy converters based on the electrostatic principle. These unique properties enable the industrial development of highly efficient and environmentally sustainable energy converters, which opens up the possibility to further exploit large renewable and inexhaustible energy sources like wind and water that are widely unused otherwise. Compared to other electroactive polymer materials, polyurethanes have certain advantages over silicones and acrylates. Due to the inherently higher permittivity as well as the higher dielectric breakdown strength, the overall specific energy, a measure for the energy gain, is better by at least factor of 10, that is, more than 10 times the energy can be gained out of the same amount of material. In order to reduce conduction losses on the electrode during charging and discharging, a highly conductive bidirectional stretchable electrode has been developed. Other important material parameters like stiffness and bulk resistivity have been optimized to fit the requirements. We also report on different measures to evaluate and improve electroactive polymer materials for energy harvesting by, for example, reducing the defect occurrence and improving the electrode behavior.