A Prototype MEMS Actuator Driven by Magnetic Fluid Enclosed with Polyimide Diaphragms

Abstract

A MEMS actuator using a magnetic fluid enclosed with polyimide (PI) diaphragms is proposed. The actuator produces a large displacement and force thanks to its structure in which a magnetic fluid is confined between two thin-film PI diaphragms (diameter: 5 mm) fabricated on two silicon substrates. The two substrates with diaphragms are glued together by sandwiching a polyester sheet to form a diaphragm unit. The thickness of the diaphragms is 8.5 µm so that they can deflect greatly. The magnetic fluid inserted between the two diaphragms is composed of magnetite and isoparaffin. The diaphragm unit (containing the magnetic fluid) is deflected by applying an external magnetic field to it with a magnet coil. Response times and displacements of the diaphragms were measured when a magnetic field was applied. Under an applied voltage of 10 V, the diaphragm unit could produce displacements of 4 µm at the diaphragm center. Response time to reach 90% of the maximum diaphragm displacement was about 2 s. Under an applied voltage of 80 V, force generated by the diaphragm unit was 0.065N. It is concluded from these experimental results that the proposed actuator is applicable to MEMS devices such as micro pumps and give another example here.