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A microfluidic rectifier: anisotropic flow resistance at low Reynolds numbers
Alex Groisman1, Stephen R Quake
1Department of Applied Physics, California Institute of Technology, MS 128-95, Pasadena, California 91125, USA.
Physical Review Letters
|April 20, 2004
Summary
Researchers developed a microfluidic rectifier, a special channel that exhibits anisotropic flow resistance. This device, utilizing non-Newtonian fluid properties, functions as a dynamic valve for microfluidic systems.
Area of Science:
- Fluid Dynamics
- Microfluidics
- Non-Newtonian Fluid Mechanics
Background:
- In microfluidic devices, low Reynolds number (Re) typically leads to linear Navier-Stokes equations and reversible, isotropic flow.
- This implies that flow resistance in microchannels is generally uniform regardless of direction.
Purpose of the Study:
- To present a microfluidic rectifier with anisotropic flow resistance.
- To demonstrate nonlinear operation at low Re using non-Newtonian fluid properties.
Main Methods:
- Designing a microchannel with a specific geometry to induce anisotropic flow resistance.
- Utilizing a 0.01% aqueous solution of a high molecular weight polymer as the working fluid.
- Investigating the flow resistance characteristics for opposite flow directions at low Re.
Main Results:
- The microfluidic rectifier exhibited strongly anisotropic flow resistance, with differences up to a factor of 2 for opposite flow directions.
- The device demonstrated nonlinear operation at low Reynolds numbers, deviating from Newtonian fluid dynamics predictions.
- The anisotropy is attributed to the non-Newtonian elastic properties of the polymer solution.
Conclusions:
- A microfluidic rectifier was successfully designed and demonstrated.
- The device functions as a dynamic valve, leveraging non-Newtonian fluid elasticity.
- Potential applications include microfluidic pumps and integrated microfluidic devices.
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