Electricity from the Ocean Waves

EPoSiL Project Manager Dr. Istvan Denes tests the demo model at Darmstadt Technical University.

Up to now, however, mass-producing parts based on dielectric elastomers has proved difficult. “What we needed most were elastic polymers with properties that had been optimized for these kinds of applications and that can be easily processed,” explains Dr. Andreas Köllnberger, the global product development manager for Engineering Silicones at WACKER. With the launch of ELASTOSIL® Film, WACKER has introduced an elastic, extremely thin film on the market that is suitable for large-scale production as rollstock, allowing manufacturers to begin mass producing EAP components. Precision silicone films are also suitable for applications beyond EAP technology, however, as they can be used as functional membranes or for dressing wounds.

Manufactured using a patent-pending process that obviates the need for solvents, these continuous films are made from addition-curing silicone rubber compounds and are commercially available in thicknesses less than 100 microns – they can even be obtained in thicknesses as low as 20 microns.

Thinner than a human hair: ELASTOSIL® Film and SILPURAN® Film – precision silicone films – are suitable for applications such as functional packaging films, wound dressings, sensors, actuators and energy-saving electrical relays.

The manufacturing process yields homogeneous, flawless films that are characterized by their extremely uniform thickness, which varies by no more than 5 percent across the entire width and length of the film web. And to ensure that no particles protrude from the film surface, the rubber blends are produced under cleanroom conditions.

Silicone films possess all the key properties for which silicones are noted, namely heat resistance, low-temperature flexibility, chemical inertness and biocompatibility. Their surface is highly hydrophobic, i.e. water-repellent, and they exhibit silicones’ typical high resistance to many different physical and chemical influences. Their favorable elastic properties also help prevent them from fatiguing under years of mechanical stress.

SILPURAN® Film

With SILPURAN® Film, WACKER has developed a high-purity version of its ultrathin, ultra-high precision silicone rubber films, which are particularly targeted at the needs of the health-care and medical industries. The silicone rubber used in these films has passed selected tests for biocompatibility according to ISO 10993 and US Pharmacopeia Class VI. SILPURAN® silicones are manufactured and packaged under cleanroom conditions in accordance with WACKER’s own standard for medical materials (WACKER CLEAN OPERATIONS) to eliminate any impurities. For example, breathable adhesive plasters that help boost the healing process can be made from SILPURAN® Film. SILPURAN® Film also offers new possibilities in medical equipment and prosthetics.

In-Plane Expansion

ELASTOSIL® film can be used, e.g., to produce deformable capacitors. This is done by coating the upper and lower surfaces of the films with a flexible, electrically conductive material. When a DC voltage is applied, the electrodes are attracted to each other due to their opposite electrostatic charges, and compress the soft film material. The layer of elastomer material becomes thinner, and spreads out in the plane. As a result, the capacitor becomes flatter and wider overall. When the capacitor is discharged, the elasticity of the film causes it to return to its original shape.

Because capacitor deformation can be repeated any number of times and systematically controlled, manufacturers can use EAP films in actuators for converting electrical voltage into movement. The reverse is also possible: EAP films can convert mechanical movement into electrical voltage. This property means that EAP technologies are suitable for producing sensors and novel types of generators. The deformable capacitor is always the base unit of the system.