Multistep sequential batch assembly of three-dimensional ferromagnetic microstructures with elastic hinges

• Published in: Journal of microelectromechanical systems Vol. 14; no. 6; pp. 1265 - 1271
• Main Authors: Iwase, E., Shimoyama, I.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.12.2005; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Assembly; Batch assembly; elastic hinges; Exact sciences and technology; Fasteners; Ferromagnetism; Ferrous alloys; Hinges; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Magnetic fields; Magnetic materials; Magnetism; Magnetoelasticity; magnetostatic torque; Mechanical instruments, equipment and techniques; Micromechanical devices and systems; Microstructure; Nickel; Nickel base alloys; Permanent magnets; Physics; Plates; Process design; sequential assembly; Three dimensional; three-dimensional (3-D) microstructures; Torque; Compliant mechanism; sequential assembly; three-dimensional (3-D) microstructures; Ferromagnetic materials; elastic hinges; Batch assembly; Permanent magnets; Experimental study; Permalloy; magnetostatic torque; Multistep method; Sequential method; Batch process; Electrodeposition; Magnetic materials; Nickel; Microelectromechanical device; High aspect ratio microstructure HARM
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2005.851814

In this paper, we have developed a process for multistep sequential batch assembly of complex three-dimensional (3-D) ferromagnetic microstructures. The process uses the magnetic torque generated by an external magnetic field perpendicular to the substrate to lift hinged structures. We found that a dimensionless factor that depends on the volume of the magnetic material and the stiffness of the hinges determines the sensitivity of the hinged microstructures to a magnetic field. This factor was used as a criterion in designing a process for sequential batch assembly, i.e., for setting appropriate differences in sensitivity. Using a dimensionless factor in the design of the sequential assembly simplified the assembly process, which requires only placing the structures on a permanent magnet, and which can be used to carry out multistep sequential batch assembly. We fabricated hinged microstructures, which consist of 4.5-/spl mu/m-thick electroplated Permalloy plates and 200-nm-thick nickel elastic hinges of various sizes. In an experiment, four plates (600 /spl mu/m/spl times/800 /spl mu/m) were lifted sequentially and out-of-plane microstructures were assembled in a four-step process. Assembly of more complex out-of-plane microstructures (e.g., regular tetrahedrons, 800 /spl mu/m long on one side) was also shown to be feasible using this method of sequential batch assembly. [1351].