Miniature diaphragm pumps with valves about the width of a human hair have been etched and assembled on silicon chips for moving fluid between reservoirs in micro-fluid systems. Advantages are easy fabrication, high reliability, and the capability for continuous pumping of pure fluids or fluids containing particulates/cellular material at flow rates of 2 to 2000 microliters/minute, and pressures up to approximately 4.75 meters of water.

• Technology: A description of our micro-pump technology in terms of commercial applications is available in a Non-Confidential Summary, Micro-Pumps Based on Valves Having No Moving Parts. The document includes information on who to contact for more information.
• Patents: United States Patents 5,876,187 "Micropumps with fixed valves" and 6,227,809 Method for Making Micropumps, which are also available via the US Patent and Trademark Office, or the IBM Intellectual Property Network.
• Publications:
  • 2000 - Journal of Micromechanics and Microengineering: C. J. Morris and F. K. Forster
    Optimization of a circular piezoelectric bimorph for a micro-pump driver, vol. 10, no. 3, pp. 459-65.
    Abstract: Piezoelectric bimorph actuation has been used successfully in numerous types of microdevices, most notably micro-pumps. However, even for the simple case of circular geometry, analytical treatments are severely limited. This study utilized the finite element method to optimize the deflection of a circular bimorph consisting of a single piezoelectric actuator, bonding material and elastic plate of finite dimensions. Optimum actuator dimensions were determined for given plate dimensions, actuator-to-plate stiffness ratio, and bonding layer thickness. Dimensional analysis was used to present the results for fixed and pinned edge conditions in a generalized form for use as a design tool. For an optimally-thick actuator, the optimum actuator-to-plate radius ratio ranged from 0.81 to 1.0, and was independent of the Young's Modulus ratio. For thin plates, a bonding layer minimally affected optimum dimensions. Optimized actuator dimensions based on a model of an actual device were within 13 percent of the fixed-edge condition.
  • 2000 - ASME: C. J. Morris and F. K. Forster, The correct treatment of harmonic pressure-flow behavior in microchannels, In Micro-Electro-Mechanical Systems (MEMS), ASME International Mechanical Engineering Congress and Exposition (Orlando), Nov. 5-10, 2000, Vol. MEMS-2, pp. 473-479. This paper utilizes the exact solution of the Navier-Stokes equations for oscillatory flow to correct deficiencies associated with more commonly-used methods.
  • 2000 - uTAS: The Effect of Particles on Performance of Fixed-Valve Micropumps. A reprint of a scientific paper on the effect of degassing procedure, and particle concentrations on the performance of fixed-valve micropumps. Presented at the 4th International Symposium on Micro Total Analysis Systems (uTAS), May 14-18, 2000, in Enschede, Netherlands.
  • 1999 - ASME: Transport of Particle-Laden Fluids through Fixed-Valve Micropumps. A scientific paper on the ability of fixed-valve micropumps to directly transport suspensions of polystyrene microspheres ranging from 3 to 20 um in diameter without clogging at densities as high as 9000 particles/ul of suspension. Presented at the American Society of Mechanical Engineers (ASME) winter annual meeting in November 14-19, 1999, in Nashville.
  • 1998 - uTAS: Impedances for Design of Microfluidics Systems. A scientific paper on our numerical simulations of microvalves. Presented at the Micro Total Analysis Systems '98 Workshop in Banff, Canada, 13-16 October 1998.
  • 1997 - ASME: Designing High-Performance Micro-Pumps Based on No-Moving-Parts Valves. Here is an HTML version. A scientific paper on our system model of a micropump. Presented at the American Society of Mechanical Engineers (ASME) winter annual meeting in November, 1997, in Dallas.
  • 1995 - ASME: Design, Fabrication and Testing of Fixed-Valve Micro-Pumps. The first scientific paper on our work presented at the American Society of Mechanical Engineers (ASME) winter annual meeting in November, 1995, in San Francisco.
• News Article: A story also appeared on the front page of the Seattle Post-Intelligencer (October 16, 1996). The Article covers the aspect of our work that is related to Nikola Tesla, the prolific inventor who patented the "valvular conduit" (Pat. No. 1,329,559) on Feb. 3, 1920.
• Poster Presentation: For more information on fabrication, principles of operation and performance, a poster presentation is available.
• Pump Animation: An animated java applet of a micro-miniature pump in action. An animated GIF (311 kB) of the velocity field in a Tesla-type T45 microvalve as it evolves through one pumping cycle. The color spectrum refers to the speed of the fluid: red is fast, violet is slow. The arrows show the direction of flow.
• Fabrication Partners: Silicon processing is performed at the Washington Technology Center (WTC) Microfabrication Laboratory . Deep Reactive Ion Etching (RIE), an essential step in the processing, is performed by staff at Stanford Nanofabrication Facility (SNF), and staff at the Minnesota Microtechnology Laboratory (MTL).
• Lab Info: Access to this link is restricted.