Micropumps/Microvavles
Outline
Different types of micropumps
Mechanic pump
Membrane pump
Diffuser pump
Non-Mechanic pump
Bubble pump
Electrohydrodynamic (EHD) pump
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
• Micro gear pump
• Diffuser pump
Pump chamber
Valves
Check valve-example
Fixed geometry valve pump
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.
Electrostatic Membrane Pump
• Goodness:
Low power, good control of actuation and short response time.
• Weakness:
High actuation voltage, small stroke.
R. Zengerle et. al., MEMS’95
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, 15:p. 153-167
Thermopneumatic Membrane Pump
• Goodness:
Large actuation force, low operating voltage.
• Weakness:
Low driving frequency
Lammerink, 1993; Lammerink, 1996
Shape Memory Alloy Driven Membrane
Pump
Suction State
• Goodness:
• Weakness:
Pumping State
Large pumping rate, high working pressure.
Low driving frequency, low energy efficiency
W.L., Benard, et. al., “A Titanium-Nickel Shape-Memory Alloy Actuated
Micropump”, Proceedings of Transducers’97, vol. 1, pp.361-364
Centrifugal pump- 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”, MEMS’s 95, 1995, pp. 408-412
Micro gear pump
Diffuser Pump
inlet
outlet
inlet
Q1
Q2
Q2
Q1
Volume
decreasing
Volume
increasing
Diffuser action
Nozzle action
Supplying Mode: |Q1|>|Q2|
•
•
outlet
Diffuser action
Nozzle action
Pumping Mode: |Q1|<|Q2|
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.
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,
Non-Mechanical Pump
• Without movable parts, non-mechanical pump is
often much simpler than mechanical pump.
• Non-mechanical pump includes:
• Electric field mediated pump
• Bubble pump
• Other pumps
Electric field mediated pump
Electric-osmotic pump
Electric-osmotic pump-example
Static EHD pump
EHD pump-example
EHD Pump
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
EHD PUMP-example
A Planar EHD Pump
flow
+ -
+ -
+ -
positive ion
+ -
+ -
+ -
flow
Si-Hong Ahn, Yong-Kweon Kim, “Fabrication and experiment of a planar
micro ion drag pump,” Sensors and Actuators A70 (1998) 1-5
Design of EHD Pump
1. Build the electrodes
and channel on the
same wafer.
2. Electrodes go across
the sidewall, resulting
in a higher efficiency.
Two Successive Pumping Photos
Fluid
Fluid
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
Bubble Pump
T.K. Jun and C.-K. kim, J. Appl. Phys., Vol. 83, No. 11, 1998
Magnetic Pump
Magnetic Pump-example
Ultrasonic pump
Acoustic pump-example
Pump by interfacial tension
Interfacial tension pump- Example