MICRO PUMPS, VALVES AND MIXERS

MICRO PUMPS, VALVES AND MIXERS

Susan Beatty

Dave Ni

Kunal Thaker

OUTLINEOUTLINE

Micro pumps Micro valves Micro mixers Keypoints (conclusion)

MICROPUMPSMICROPUMPS

GENERAL TYPES OF MICROPUMPS

GENERAL TYPES OF MICROPUMPS

BUBBLE PUMPS DIFUSSER PUMPS MEMBRANE PUMPS (most common) ROTARY PUMPS ELECTROHYDRODYNAMIC PUMPS ELECTROOSMOTIC/ ELECTROPHORETIC

PUMPS ULTRASONIC PUMPS OPTICAL PUMPS

BUBBLE/DIFUSSER PUMPBUBBLE/DIFUSSER PUMP

The formation and collapse of a bubble in the liquid is used to drive the flow of the liquid

Allows for a valve-less diffuser design Greatly enhances mixing of the constituent

phases Flow rate in the range of 4-5 μL/sec for 250-

400Hz

http://www.me.berkeley.edu/~lwlin/papers/2002Tsai.pdf

MEMBRANE PUMPSMEMBRANE PUMPS Method of displacing the membrane

– Magnetically– Electrostatically– With a piezoelectric– Thermally (SMA and thermopneumatically)

Sensitive to blockage by particulates in the fluid Flow rate in the range of 100-10000 μL/sec

http://ej.iop.org/links/60/IYwveEquvuX,ovtuKcQOMw/jm8218.pdf http://www.ajou.ac.kr/~mems/proj-1-1.htm

ROTARY PUMPSROTARY PUMPS Very rare and not commonly researched Extremely complicated fabrication process High susceptibility to failure Very precise control of the fluid flow and direction Good for transporting high impurity liquids

http://cmmt.gatech.edu/Mark/Publications/Allen_95_Fluid_Micropumps_Rot_Mag_Actu.pdf

ELECTROHYDRODYNAMIC PUMPS

ELECTROHYDRODYNAMIC PUMPS

Uses an applied electric field on the fluid to be pumped to induce charge and also to electrostatically move the induced charges

Not suitable for the delivery of most biological fluids, as a very specific fluid conductivity is required

Extremely high voltages are required to move the fluids (~700volts)

Has an equivalent magnetohydrodynamic pump

ELECTROOSMOTIC/ ELECTROPHORETIC

PUMPS

ELECTROOSMOTIC/ ELECTROPHORETIC

PUMPS Electrophoretic pumping relies on the presence of ions in the fluid

– The ions are manipulated through the application of an electric field and flow is induced

Electroosmotic flow relies on the presence of ions on the surfaces of the fluidic channel Example- between glass and organic fluids– An applied electric field allows for the movement of the bulk fluid

Flow rate on the order of 15 μL/sec No moving parts

http://www.stanford.edu/~chenaiwa/Micropump_Jmems.pdf

ULTRASONIC/OPTICAL PUMPS

ULTRASONIC/OPTICAL PUMPS

Ultrasonic pumps use piezoelectric networks to actuate on a cyclical basis to produce predictable fluid motion– Most applicable to mixing, not pumping

In optical pumps, heat is introduced to the fluid by way of optical absorption– Gradients in the fluids heat result in viscosity

and surface tension gradients, which in turn lead to fluid flow by way of the thermocapillary effect

– Most applicable to mixing, not pumping

VALVESVALVES

VALVE CLASSIFICATIONVALVE CLASSIFICATION

Non-moving valve Passive valves Actuated valves

NON_MOVING VALVESNON_MOVING VALVES

Diffuser Valve– Provides

directional resistance

http://www.cr.org/publications/MSM2001/html/T67.02.html

PASSIVE VALVESPASSIVE VALVES

Cantilever

Disc

Membrane

Shoji, Journal of micromechanics and microengineering 1994

PASSIVE VALVES (con’t)PASSIVE VALVES (con’t)

Piston

Gas controlledhttp://www.ca.sandia.gov/microchem/microfluidics/valves/valves1.html

Quake, Science 2000

ACTIVE VALVESACTIVE VALVES

Valve types based on actuation– Electromagnetic– Piezoelectric– Pneumatic– Shape memory alloy– Thermopneumatic– Chemical

MICROMIXERSMICROMIXERS

Definition: The controlled micro-mixing of two or more fluids

GENERAL TYPES OF MIXERS

GENERAL TYPES OF MIXERS

Laminating Mixers

Plume Mixers

Active Mixers

Micrograph of Silicon-glass -- Copyright, Meinhart, Bayt  1998

http://www.engineering.ucsb.edu/~nari/mycurrentresearch.htm

LAMINATING MIXERSLAMINATING MIXERS

At the microscopic scale the use of laminating mixers is try to “laminate” two or more fluids together to increase the contact area and enhance diffusion (0.5 to 12 l/min)

Two fluids entering the inlet ports laminate at the first horizontal junction, producing two side-by-side fluid streams. Successive vertical separation and horizontal reuniting of fluid streams increases the

number of laminates with each stage and, thus, the contact area between the two fluids.

http://transducers.stanford.edu/stl/Projects/fluidic-charact.html

PLUME MIXERSPLUME MIXERS

Takes advantage of the behavior of a fluid leaving a narrow nozzle (15m)

Generates a small plume which increases the contact area of two liquids

Homogeneous mixing in 1.2 secs in a 0.5 l volume at a 45 l/min flow rate

ACTIVE MIXERSACTIVE MIXERS

The use of external energy– Ultrasonic traveling wave pumps

moving fluids in a circulating path

– Bubble pumps – two large pumps used to generate push & pull forces

KEY POINTSKEY POINTS Membrane pumps are the most common type of

micro pumping device currently fabricated An attempt is being made to phase out check

valves and other mechanisms that slow down the frequency response of the pumping system.– Drive toward diffuser valves

More flow loss, but increase in frequency. Pumps with non-moving parts are preferred due to

higher reliability, etc. Bubble, electroosmotic, and electrophoretic pumps

tend to be the direction in bio-micro fluidics applications.

KEY POINTS (con’t)KEY POINTS (con’t)

Passive valves are commonly used because they are easier to fabricate and are smaller that actuated valves

The easier and cheaper the valve is to fabricate the more likely it will be used

Chemically reactive valves are ideal for bio-microfluidics because they are easy to make, they are small and they behave as an active valve

KEY POINTS (con’t)KEY POINTS (con’t)

Laminating Mixers – to laminate fluids together

Plume Mixers – plume is generated to increase contact area of two liquids

Active Mixers – uses external energy to mix fluids