Efficient magnetic microactuator with an enclosed magnetic core

An efficient spiral-type magnetic microactuator design, composed of an enclosed core and a magnetic plate, is presented to produce a high magnetic flux density, a large force, and a large displacement. The design allows a large variation in area of the Permalloy plate and then the area of the poles can optimally enlarge with the fixed area of the Permalloy plate. Verification by the magnetic path analysis and the finite element method yields a theoretical actuator design for the magnetic microactuator. An integrated magnetic microactuator is fabricated and tested to demonstrate the capability of the improved design. The microactuator consists of an electromagnet and a four-suspended-beam structure, bound together with a 28-μm-thick spacer between them. A series of experiments determines that the measured stiffness of the four-beam structure is approximately 45 μN/μm. Notably, the Permalloy plate on the four-suspended-beam structure is moved by 27.6 μm at a current and voltage of 292 mA and 4.5 V, respectively. The estimated force produced by the microactuator is around 1240 μN. These results show the microactuator with an enclosed core is efficient in producing magnetic force and has flexibility in application.