At the last trade fair three years ago, WACKER introduced precision silicone films for the first time. Since then, the interest in the product innovation has been undiminished. The Munich-based chemical group has evaluated more than 450 inquiries, and numerous projects have emerged.
At this year's K, WACKER is presenting the first specific applications, with a particular focus on novel textile sensors. This application exploits the electroactive properties of silicone. The ultrathin high-precision film is embedded between two conductive electrodes made of carbon-black-filled silicones. Together, the layers form a flexible capacitor that can store electric charge. If the silicone capacitor is mechanically deformed – for example due to a tensile or compressive movement – its capacitance also changes. The subtle nuances of these capacitance changes can be measured and thus used for sensory purposes, for example to make body movements visible.
ELASTOSIL® Film is made in cleanroom conditions without the use of solvents. WACKER's patented production process creates extremely thin and faultless silicone films in thicknesses of between 20 and 400 micrometers. The film thickness across the entire width and length of the film web deviates from specification by +/- 5 percent at most. This and the typical silicone properties of the elastomer enable technical applications that could not previously be realized on an industrial scale.
Like all silicone elastomers, ELASTOSIL® Film is also an electroactive polymer (EAP) due to its dielectric properties. Silicone films are capable of responding to electrical stimulation under certain circum-stances. This is the case, for example, when the elastomer is situated between two ductile and flexible electrodes. The silicone forms a dielectric layer. It does not conduct current, but it is permeable to electric fields.
Together, the silicone layer and electrodes form a flexible capacitor. When a DC voltage is applied, the electrodes are electrostatically attracted to each other, and compress the soft film material. The film becomes thinner, and spreads out in the plane. The capacitor thereby becomes flatter and wider overall. When the capacitor is discharged, the elasticity of ELASTOSIL® Film causes it to return to its original shape.
This property renders silicones particularly attractive for the following key electroactive technologies:
- Sensors: Sensors made from ELASTOSIL® Film can measure movement in clothing or gloves. This enables movements to be displayed virtually, for example on a computer or smartphone. These types of sensor, also called “wearables”, are in great demand in consumer electronics as well as in fields such as health, rehabilitation and sport. Using the same principle, it is also possible to control gripping tools or robots remotely.
- Actuators: ELASTOSIL® Film provides manufacturers of electrical drive components, or actuators, with entirely new possibilities. In this case, following the same electroactive principle, electricity is converted into movement. The entire process is silent and can be repeated as often as desired. These properties can be selectively exploited to develop new products and technologies, for instance for pumps, switches, valves, electric relays, artificial muscles or even loudspeakers.
- Generators: If several hundred silicone-film capacitors are stacked on top of each other it is even possible to generate electricity from motion. Silicone films thus allow novel electrical generators to be developed.
In future, silicone films could also be an important consideration in membrane technology. Silicones hold back water, but grant free passage to water vapor and certain gases. ELASTOSIL® Film does this highly selectively: carbon dioxide, oxygen and water vapor pass through quicker than nitrogen. A membrane made from ELASTOSIL® Film can therefore be used to separate gases, for instance to remove a specific gas such as carbon dioxide.
Visit WACKER at K 2016 in Hall 6, Booth A10.