ElectroMechanical Film (EMFi): A new multipurpose electret material

Mika Paajanen (Corresponding Author), Jukka Lekkala, Kari Kirjavainen

Research output: Contribution to journalArticleScientificpeer-review

244 Citations (Scopus)


The ElectroMechanical Film (EMFi) is a thin, cellular, biaxially oriented polypropylene film that can be used as an electret. Having a special voided internal structure and high resistivity, it is capable of storing large permanent charge. The charge is injected by a corona method using ∼10 kV cm−1 fields, thus creating internal electrical discharges inside the cellular structure. Films of different thickness and elasticity can be manufactured. The thickness in sensor and actuator applications is typically 30–70 μm. When metallized on both sides, EMFi is capable of measuring pressure and force changes offering large application potential in different fields of technology including microphones and also actuators. New loudspeaker panels based on EMFi are only a few millimeters thick.
Original languageEnglish
Pages (from-to)95 - 102
Number of pages8
JournalSensors and Actuators A: Physical
Issue number1-2
Publication statusPublished - 2000
MoE publication typeA1 Journal article-refereed

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