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Browse Prior Art Database

MICROMECHANICAL CHECK VALVE

IP.com Disclosure Number: IPCOM000007390D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2002-Mar-21
Document File: 3 page(s) / 134K

Publishing Venue

Motorola

Related People

Jon T Fitch: AUTHOR

Abstract

The problem ofcontrolling fluid (gas and liquid) flow on a microscopic' scale is addressed. Applica- tions include controlling the flow of blood in small capillaries, and, membranes which are porous in only one direction. Several excellent articles have been written about the problem of manipulating fluids on a microscopic scale [l, 21. Due to the interest in ink jet printing technology, quite a bit of work has already been done on micromachining nozzles in silicon [3].

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MOTOROLA Technical Developments Volume 24 March 1995

MICROMECHANICAL CHECK VALVE

by Jon T Fitch

valves could be fabricated so as to make a porous membrane which is porous in only one direction (see Figure 5).

INTRODUCTION

  The problem ofcontrolling fluid (gas and liquid) flow on a microscopic' scale is addressed. Applica- tions include controlling the flow of blood in small capillaries, and, membranes which are porous in only one direction. Several excellent articles have been written about the problem of manipulating fluids on a microscopic scale [l, 21. Due to the interest in ink jet printing technology, quite a bit of work has already been done on micromachining nozzles in silicon [3].

ADVANTAGES

  The proposed micromechanical check valve has the following unique attributes: (1) conventional sem- iconductor fabrication techniques are used, (2) the only limit on the size of the valve is photohthogra- phy, (3) an array of micromechanical check valves would provide a membrane which is porous in only one direction, (4) the valve could be constructed with any number of polymer flaps-the fabrication diagrams show 4 but other numbers could be used, and (5) this valve could be fabricated on a wide array of substrate materials such as quartz, nitride, met- als, and plastics with the appropriate choice ofsacri- licial materials (e.g. a metal instead ofTEOS).

INVENTION AND PROBLEM SOLUTION

  One of the most basic elements necessary for controlling fluid flow is a check valve. A check valve is usually an in-line valve which permits fluid flow in only one direction. Thus, this type of valve is essential to prevent unintended backstreaming in a fluid control system. The invention proposed here is a microscopic check valve fabricated From polymeric or other flexible materials. In this invention, a cav- ity is etched all the way through a silicon wafer, stopping on a thin membrane ofsilicon dioxide. Fol- lowing this a thin etch stop layer of amorphous sili- con is deposited, followed by a very thick layer of silicon dioxide such as TEOS (see Figure 1). The TEOS is patterne...