AVS 45th International Symposium
    The Science of Micro-Electro-Mechanical Systems Topical Conference Monday Sessions
       Session MM+VT-MoA

Paper MM+VT-MoA8
Novel Microvalve with Low Leakage

Monday, November 2, 1998, 4:20 pm, Room 324/325

Session: Vacuum MEMS and Microanalysis
Presenter: M. Hirano, Nippon Telegraph and Telephone Corporation, Japan
Authors: M. Hirano, Nippon Telegraph and Telephone Corporation, Japan
K. Yanagisawa, Nippon Telegraph and Telephone Corporation, Japan
S. Nakano, NTT Advanced Technologies Corporation, Japan
M. Shoji, Nippon Telegraph and Telephone Corporation, Japan
Correspondent: Click to Email
Microvalve, being capable of precisely controlling fluid flow, is necessary in various industrial fields such as chemical analysis. This paper reports the novel microvalve with very low leakage, which was fabricated by silicon micromachining techniques. The valve is a micromachine constructed on a silicon substrate chip, and it uses a valve cap supported by a suspension spring and a valve seat with a 50-µmm-diameter bore to control fluid flow. Normally closed valve is obtained by applying compressive stress to the suspension spring @footnote 1@. Piezoelectric actuator bends the suspension spring, resulting in opening and closing the valve. The silicon substrate chip, on which the microvalve was fabricated, was suitably mounted on the specially designed holder, to which inlet and outlet lines are connected. The leak or flow conductance of the microvalve was precisely determined by measuring the pressure change in the gas flow system designed for precisely determining the leak and flow rate @footnote 2@. The measurements show that the valve has a very low leak rate of 5.8 x 10@super -10@ Pam@super 3@/s. This reduced leakage was due to tight contact between the cap and seat, which was obtained by nanometer-scale flat valve surfaces and self-alignment of the cap and seat-bore based on the fabrication techniques we have developed @footnote 1@. It is concluded that the flat surfaces result from the flat substrate of the sacrificial SiO@sub 2@ film deposited by RF magnetron sputtering, and from the homogeneous dry-etching at our amorphous surfaces by ion-beam milling. @FootnoteText@ @footnote 1@ K. Yanagisawa, H. Kuwano, and A. Tago, Microsystem Technologies 2. 22 (1995). @footnote 2@ M. Hirano, K. Yanagisawa, H. Kuwano, and S. Nakano, Trans. IEE of Japan 117-E, 622 (1997).