A micropillar-based microfluidic viscometer for Newtonian and non-Newtonian fluids

Area of Science:

• Materials Science
• Fluid Mechanics
• Biomedical Engineering

Background:

• Accurate viscosity measurement is crucial for characterizing fluids.
• Existing methods can be complex or require large sample volumes.
• Developing portable, sensitive viscometers is an ongoing challenge.

Purpose of the Study:

• To introduce a novel viscosity measurement technique using flexible micropillars.
• To demonstrate the method's applicability to both Newtonian and non-Newtonian fluids.
• To assess the potential for a portable microfluidic viscometer.

Main Methods:

• Fabrication of flexible (poly)dimethylsiloxane (PDMS) micropillars.
• Measurement of micropillar deflection under fluid flow.
• Development of a calibration curve based on nonlinear deflection-viscosity relationship.
• Validation with glycerol/water solutions and human whole blood samples.

Main Results:

• A nonlinear relationship between fluid viscosity and micropillar deflection was observed due to PDMS viscoelasticity.
• The method accurately measured viscosity of Newtonian fluids (2-100 cP) and non-Newtonian whole blood (2.7-5.1 cP).
• Results for whole blood showed good agreement with conventional rotational viscometers.

Conclusions:

• The novel micropillar deflection technique offers a sensitive (better than 0.5 cP) and accurate method for viscosity measurement.
• This approach has significant potential for development into a portable microfluidic viscometer for real-time rheological studies.