Emfit Ltd is manufacturer of electro-responsive ferroelectret sensors. These film-like sensors can be used for various applications, for example non-body-contact vitals signs monitoring, dementia care, actigraphs, visitor count and keypads. The sensor material 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). The biaxially stretched material is further expanded to over double of its original thickness in high-pressure gas-diffusion process. The structure of Emfit material consists of flat voids separated by thin polyolefin layers. The voids are made by compounding small particles that function as rupture nuclei, and form closed lens like cavities to the film during the biaxial orientation. A permanent electric charge is injected into the material using a corona charging process. The voided internal structure makes the film soft and elastic in the thickness direction. This means that the voids expand and contract in relation to the orientation of the film. The excellent sensor and actuator operations of Emfit film are based on the fact that reduction in the thickness of the film caused by an external force takes place in the gas voids and these are much softer than the polymer layers.
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Räisänen, L., Räisänen, H. Electro-responsive Polymer and its Sensor Applications. MRS Online Proceedings Library 889, 201 (2005). https://doi.org/10.1557/PROC-0889-W02-01