A picoliter-volume mixer for microfluidic analytical systems.

Area of Science:

• Microfluidics
• Electrokinetics
• Chemical Engineering

Background:

• Efficient mixing of liquid streams is crucial for microfluidic applications.
• Traditional diffusion-based mixing is slow and inefficient in microchannels.
• Electroosmotic flow (EOF) offers a controllable method for fluid manipulation in microdevices.

Purpose of the Study:

• To design and characterize a microfluidic mixer for rapid liquid stream mixing.
• To investigate mixing efficiency in a device utilizing EOF and a specific channel geometry.
• To evaluate the performance of a 100-pL mixer for microscale fluidic operations.

Main Methods:

• Fabrication of a microfluidic device with intersecting channels of bimodal width distribution (5 µm and 27 µm).
• Utilizing electroosmotic flow for liquid transport within the microchannels.
• Characterization of mixing efficiency using confocal microscopy and CCD detection.
• Performing theoretical simulations to model mixing behavior.

Main Results:

• Minimal mixing observed in the initial mixer inlet channel, relying primarily on diffusion.
• Complete mixing achieved after fluid passage through the microfabricated channel network (approx. 200 µm length).
• The bimodal channel width distribution and intersecting design significantly enhanced mixing rates.

Conclusions:

• The developed microfluidic mixer effectively achieves rapid and complete mixing of liquid streams.
• The device design, leveraging EOF and specific channel geometry, overcomes diffusion limitations in microfluidics.
• This technology holds promise for various microfluidic applications requiring efficient sample manipulation.