Magnetoelastically actuated MEMS device and methods for its manufacture
A magnetoelastically actuated device includes a microscale cantilever arm supported at a standoff distance from a substrate. The cantilever arm is formed as a laminar magnetic actuator configured to bend when it is subjected to a magnetic field. The cantilever arm includes a film of magnetostrictive material. Also provided is a method for fabricating the magnetoelastically actuated device. The method includes defining an actuator mold in a layer of photoresist on a structural layer of the cantilever arm and electrodepositing a layer of a magnetostrictive alloy containing cobalt and iron onto the structural layer within the actuator mold.
1. An apparatus, comprising:
a substrate; and
a microscale cantilever arm supported at a standoff distance from the substrate;
wherein said arm comprises a laminar magnetic actuator configured to bend the arm when subjected to a magnetic field; and wherein:
the laminar magnetic actuator comprises a film of magnetostrictive material;
the laminar magnetic actuator is a magnetic bimorph comprising a structural layer of copper underlying and adjacent to the film of magnetostrictive material;
the copper structural layer has a thickness in the range 0.5-20 μm; and
the film of magnetostrictive material has a thickness in the range 0.5-5 μm.
2. The apparatus of claim 1 , wherein the standoff distance is in the range 0.5-2 μm.
3. The apparatus of claim 1 , wherein said film is electrodeposited and has a composition that comprises cobalt and iron.
4. The apparatus of claim 1 , wherein the magnetostrictive material has a composition comprising 70-80 at. % cobalt and 20-30 at. % iron.
5. The apparatus of claim 1 configured as a variable capacitor, the apparatus further comprising a fixed electrode positioned on the substrate facing the cantilever arm, whereby a capacitance between the fixed electrode and the cantilever arm varies in response to bending of the cantilever arm.
6. The apparatus of claim 5 , wherein the standoff distance, an area of the fixed electrode, and a moveable electrode area of the cantilever arm are configured to provide a capacitance that is variable over at least the range from 1 picofarad to 5 picofarads.
7. The apparatus of claim 1 configured as an electrical switch, the apparatus further comprising a fixed electrode positioned on the substrate, whereby contact between the fixed electrode and the cantilever arm closes a circuit in response to bending of the cantilever arm.
8. The apparatus of claim 1 configured as an optical switch, the apparatus further comprising a specularly reflective coating deposited on a surface of the cantilever arm distal the substrate, whereby a light beam reflected from the specularly reflective coating is deflected in response to bending of the cantilever arm.
9. The apparatus of claim 1 , further comprising a magnetic source positioned in proximity to the laminar magnetic actuator so as to subject the laminar magnetic actuator to a magnetic bias field.
10. The apparatus of claim 1 , wherein the substrate comprises a base layer of silicon.
11. The apparatus of claim 1 , further comprising an electrostatic actuation electrode positioned on the substrate.