A Microfluidic Prototype for High-Frequency, Large Strain Oscillatory Flow Rheometry.

Area of Science:

• Fluid Mechanics
• Rheology
• Microfluidics

Background:

• Traditional rheometers often require large sample volumes and can be affected by inertial effects.
• Characterizing fluid behavior under oscillatory flow is crucial for understanding complex material properties.

Purpose of the Study:

• To introduce and validate a microfluidic device, the Rheo-chip, for rheological measurements.
• To assess the performance of the Rheo-chip in characterizing model fluids under oscillatory flow.
• To identify and model non-ideal effects impacting measurements at higher frequencies.

Main Methods:

• Development of a "Rheo-chip" device for microfluidic rheology.
• Oscillatory flow experiments with deionized water at frequencies up to 80 Hz.
• Introduction of a simplified model to account for back force and dead volume effects.

Main Results:

• The Rheo-chip successfully characterized fluids with low sample consumption (<1 mL) and minimal inertial effects.
• Measured pressure drop deviated from Newtonian predictions at frequencies ≥ 3 Hz.
• A proposed model effectively captured the frequency response of pressure drop and phase delay.

Conclusions:

• The Rheo-chip offers a promising platform for microfluidic rheology.
• Inertial and dead volume effects must be considered for accurate high-frequency rheological measurements.
• The developed model enhances the characterization of non-Newtonian fluids using this technology.