Mixing in microchannels based on hydrodynamic focusing and time-interleaved segmentation: modelling and experiment

Area of Science:

• Microfluidics
• Chemical Engineering
• Analytical Chemistry

Background:

• Efficient mixing is crucial in microfluidic devices.
• Traditional micromixers face limitations in speed and quality.
• Hydrodynamic focusing and time-interleaved segmentation offer potential solutions.

Purpose of the Study:

• To investigate a micromixer combining hydrodynamic focusing and time-interleaved segmentation.
• To theoretically model and experimentally validate the mixing performance.
• To reduce mixing path, shorten mixing time, and enhance mixing quality.

Main Methods:

• Development of a time-dependent 2D analytical model.
• Fabrication of a four-layer polymer micromixer using CO2 laser machining.
• Implementation of time-interleaved segmentation with piezoelectric valves.
• Utilizing sheath streams for hydrodynamic focusing.
• Designing a synchronized measurement setup for transient concentration field capture.

Main Results:

• The focused width is adjustable via flow rate ratio.
• Axial mixing path and segment length are controllable by switching frequency and flow velocity.
• Mixing ratio is tunable using flow rate ratio and pulse width modulation.
• Experimental concentration profiles qualitatively match the analytical model predictions.

Conclusions:

• The combined hydrodynamic focusing and time-interleaved segmentation approach significantly enhances mixing.
• The analytical model and fabricated micromixer are suitable for studying Taylor-Aris dispersion.
• This technology offers a promising platform for microfluidic mixing applications.