Emfit Ferro-Electret Film

The core competence of the Emfit sensor products is the innovative, patented Emfit film. It has a unique, strong electromechanical response. The film is based on a polyolefin material manufactured in a continuous biaxial orientation process that stretches the film in two perpendicular directions (machine direction and the transverse direction). Further the film is expanded in thickness at high-pressure gas-diffusion-expansion (GDE) process.

The structure of Emfit film consists of flat voids separated by thin polyolefin layers. Typically Emfit film is 70-80 µm thick. The voids are made by compounding small particles, which function as rupture nuclei and form closed lens like cavities to the film during the biaxial orientation. The voids are enlarged at GDE process.

The patented GDE process more than doubles the thickness and elasticity of the film by increasing the size of air-voids inside it. Electromechanical response with GDE processed film is over 10-fold compared to non-swelled film.

A permanent electric charge is injected into the material by corona charging it in high electric field. This causes electric breakdowns occur inside the material, thus charging the void interfaces inside the film in order to form an electret material capable of interacting with its environment. Thin metal electrodes are for example arranged by screen-printing them first to 75-100 µm polyester film and laminating together with Emfit film. Vacuum evaporation to both surfaces of the film is also possible for actuator purposes. Other typical ways to arrange electrodes is using aluminium-polyester laminate and etching the electrode pattern prior laminating with Emfit film.


We sell Emfit film in small sheets for research. For commercial production use we sign licence and delivery agreement where use and cost are agreed.