Feature characterization of microfabricated microfluidic chips by PDMS replication and CCD imaging

Area of Science:

• Microfluidics
• Metrology
• Materials Science

Background:

• Accurate characterization of microfluidic devices is crucial for their performance and reliability.
• Traditional metrology methods can be destructive or introduce distortions, especially for complex microstructures.
• There is a need for non-destructive, cost-effective, and precise techniques for microfeature metrology.

Purpose of the Study:

• To present a novel approach for the metrological characterization of microfabricated features on microfluidic chips.
• To validate the accuracy and reliability of the proposed method against established techniques.
• To demonstrate the advantages of the new method in avoiding profile distortions.

Main Methods:

• Utilizing poly(dimethylsiloxane) (PDMS) replication to create a mold of the microfluidic chip.
• Sectioning the PDMS replica to expose the cross-section of microfabricated features.
• Employing charge-coupled device (CCD) imaging under a microscope for profile capture.
• Applying specialized algorithms for CCD image calibration and edge detection to obtain measurements.

Main Results:

• Depth and width measurements showed good agreement with stylus profiler and universal measuring microscope data.
• The deviation between the new method and traditional techniques was less than 0.9 µm.
• The method successfully avoided profile distortions observed with stylus profilers for deeper structures.

Conclusions:

• The combined PDMS replication and CCD imaging technique provides a reliable, non-destructive, and accurate method for microfluidic chip metrology.
• This approach is cost-effective and simple to implement in standard analytical laboratories.
• The method overcomes limitations of existing techniques, offering improved accuracy for microfeature characterization.