Micropumps

1
Micropumps
Jie Su
2
Outline

• Introduction
• Different types of micropumps
• Mechanic pump
• Membrane pump
• Diffuser pump
• Non-Mechanic pump
• Bubble pump
• Electrohydrodynamic (EHD) pump
• Summary

3
Introduction

• Micropumps play a significant role in
  microfludical systems of MEMS.
• Micropumps were started in middle 1980s.
• Before 1990s, mechanical pumps were mainly
  studied. After 1990s, non-mechanical pumps were
  introduced.
• Presently most micropumps aim to fluid pumping.

4
Mechanical Pump

• In general, mechanical pump consists of moveable
  components, such as moveable valves, moveable
  membrane, moveable channel, etc.
• Mechanical pump can be categorized into
• Membrane pump
• Rotary pump
• Diffuser pump

5
Membrane Pump

• Membrane Pump often consists of two check valves
  and a chamber with moveable membrane.
• By some mechanisms, membrane can be actuated to
  change the volume of chamber.
• Because the check valve can be opened only in one
  direction, for each circle, some fluid will be
  moved from inlet to outlet.

6
Electrostatic Membrane Pump

• Goodness
• Low power, good control of actuation and short
  response time.
• Weakness
• High actuation voltage, small stroke.

R. Zengerle et. al., MEMS95
7
Pieozelectric Membrane Pump

• Goodness
• Large actuation force, and short response time.
• Weakness
• Low working frequency, small stroke.

V. Lintel et al., Sensors and Actuators A, 1988,
15p. 153-167
8
Thermopneumatic Membrane Pump

• Goodness
• Large actuation force, low operating voltage.
• Weakness
• Low driving frequency

Lammerink, 1993 Lammerink, 1996
9
Shape Memory Alloy Driven Membrane Pump
Suction State
Pumping State

• Goodness Large pumping rate, high working
  pressure.
• Weakness Low driving frequency, low energy
  efficiency

W.L., Benard, et. al., A Titanium-Nickel
Shape-Memory Alloy Actuated Micropump,
Proceedings of Transducers97, vol. 1, pp.361-364
10
Rotary Pump

• Magnetically driven
• Magnetic stator and central pin are permalloy
• Rotors were separately made and assembled into
  pump by hand (50 microns tall, 500 microns
  diameter).
• Problems are the complex fabrication process and
  reliability.

C.H. Ahn and M.G. Allen, Fluid Micropumps Based
on Rotary Magnetic Actuators, MEMSs 95, 1995,
pp. 408-412
11
Diffuser Pump

• Difference between diffuser pump and membrane
  pump is that diffuser pump has no check valves.
  Instead, two diffusers are introduced.
• Diffuser is a channel with a increasing cross
  sectional area. When fluid flows in one way or
  the other, it will encounter different flow
  resistances caused by the diffuser.

12
Diffuser Pump

• Except the difference between diffusers and
  valves, diffuser pump is similar with membrane
  pump.
• Many mechanisms can be used to drive a diffuser
  pump.
• Goodness simple fabrication, free of valve
  fatigue.
• Weakness sensitive to bubbles, low operating
  pressure

Stemme et al., 1993,
13
Non-Mechanical Pump

• Without movable parts, non-mechanical pump is
  often much simpler than mechanical pump.
• Non-mechanical pump includes
• EHD pump
• Bubble pump
• Other pumps

14
EHD Pump

• EHD pump uses applied electric field to induce
  and drag charges in fluid.
• Goodness no moving parts, very simple
  fabrication process
• Weakness unsuitable for conductive fluid

15
A Planar EHD Pump
Si-Hong Ahn, Yong-Kweon Kim, Fabrication and
experiment of a planar micro ion drag pump,
Sensors and Actuators A70 (1998) 1-5
16
Our Design of EHD Pump

• Build the electrodes and channel on the same
  wafer.
• Electrodes go across the sidewall, resulting in a
  higher efficiency.

17
Two Successive Pumping Photos
Fluid
Fluid
18
Simplest Pump Bubble Pump

• Goodness simple
• Weakness low flow rate, and fluid will be
  overheated near the heater.

T.K. Jun and C.-K. kim, J. Appl. Phys., Vol. 83,
No. 11, 1998
19
Bubble Pump
T.K. Jun and C.-K. kim, J. Appl. Phys., Vol. 83,
No. 11, 1998
20
Summary

• Many kinds of micropump are fabricated
• No perfect micropump exists. Each micropump has
  its weakness and goodness.
• More work need to be done.