AVS 46th International Symposium
    The Science of Micro-Electro-Mechanical Systems Topical Conference Thursday Sessions
       Session MM+VT-ThA

Paper MM+VT-ThA7
Design and Fabrication of an Electromagnetically Driven Microvalve for Micro Total Analysis Systems

Thursday, October 28, 1999, 4:00 pm, Room 620

Session: Vacuum MEMS
Presenter: M. Shoji, Nippon Telegraph and Telephone Corporation, Japan
Authors: M. Shoji, Nippon Telegraph and Telephone Corporation, Japan
K. Yanagisawa, Nippon Telegraph and Telephone Corporation, Japan
M. Hirano, Nippon Telegraph and Telephone Corporation, Japan
S. Nakano, NTT Advanced Technologies Corporation, Japan
Correspondent: Click to Email
Microvalves that control fluid flow over a wide flow rate range, and that are compactly assembled, are in great demand for µTAS, such as micro gas chromatographs. This paper reports on design considerations concerning the electromagnetic actuation and the fabrication of a microvalve that operates at a pressure difference of more than 1 x 10@super 5@ Pa with very low leakage. The valve is fabricated using silicon micromachining techniques.@footnote1,2@ The target specifications are a maximum flow rate of 10@super -1@ Pa m@super3@ s@super -1@, a leak rate of 10@super -9@ Pa m@super 3@ s@super -1@, a maximum power consumption of less than 0.1 W at a pressure difference of 10@super 5@ Pa, and a size of 4 x 4 x 2 mm including the actuation unit. The microvalve has a disk-shaped 1-µm-thick cap with a diameter of 100 µm. Actuation of the valve requires a force of more than 1.5 mN perpendicular to the surface of the cap and a stroke of 5-10 µm. To achieve this actuation, ferromagnetic material is deposited (electroplated) onto the cap and an electromagnet (1.3 x 1.5 x 3.2 mm) is set above the cap to generate an attractive force on the ferromagnetic material. The design parameters were determined by three-dimensional numerical analysis that took account of the nonlinear B-H curves of magnetic materials. When the deposited material was Ni with a thickness of 100 µm, and the distance from the Ni to the magnet was 20 µm, a sufficient force was attained if the formed Ni area was several times larger than the cap area. The analysis also showed that using materials with a higher saturation magnetization than Ni would increase the force, thus enabling the valve to work at a higher pressure difference. The effects of such materials will also be reported. @FootnoteText@ @footnote1@K. Yanagisawa, H. Kuwano, and A. Tago, Microsystem Technologies 2, 22 (1995). @footnote2@M. Hirano, K. Yanagisawa, H. Kuwano, and S. Nakano, Proc. IEEE Micro Electro Mechanical Systems, p. 323 (1997).