Electromechanical Film (EMFI, EMFIT, trademarks of Emfit Ltd) is a thin, flexible film that can function as a sensor or actuator. It is composed of a charged polymer coated with two conductive layers, making it an electret. It was invented and first made by Finnish inventor Kari Kirjavainen. Its voided internal structure and high resistivity allow it to hold a high electric charge and make the film very sensitive to force. Changes in the films thickness create an electric charge and make it operate as a sensor, or when an electric voltage is applied, it can function as an actuator. This gives the film applications in different fields of technology, including, but not limited to, mechanical vibration and ultrasound sensors, microphones, loudspeaker panels, keyboards, and physiological touch sensors. Other than being cheap, its main advantage is its versatility; it can be cut, reshaped, and resized depending on its surface of application.