Simple Multi-level Microchannel Fabrication by Pseudo-Grayscale Backside Diffused Light Lithography.

Area of Science:

• Microfluidics
• Photolithography
• Biotechnology

Background:

• Multi-level channel fabrication in microfluidics is often expensive and time-consuming.
• Traditional grayscale photolithography requires costly masks and is typically used with less common positive photoresists for microfluidic prototyping.

Purpose of the Study:

• To develop a simple, inexpensive, and accessible method for fabricating multi-level microfluidic channels.
• To demonstrate the utility of this new method for cell separation applications.

Main Methods:

• Utilized pseudo-grayscale (pGS) photomasks with backside diffused light lithography (BDLL).
• Employed commonly used negative photoresist SU-8 and standard laboratory equipment (hot plates, UV transilluminator).
• Fabricated weir-type cell traps through a single UV exposure.

Main Results:

• Successfully created smooth, multi-level channels with gradually changing heights without true grayscale masks.
• Demonstrated the ability to fabricate stable microfluidic structures from unspun photoresist layers.
• Achieved efficient separation of cancer cells from red blood cells and larger cell clusters using the fabricated cell traps.

Conclusions:

• pGS BDLL offers a cost-effective and simple alternative for microfluidic fabrication, aligning with the 'garage microfluidics' concept.
• The method's compatibility with basic laboratory equipment lowers the barrier to entry for microfluidic research and development.
• The demonstrated cell separation capabilities highlight the practical applicability of this novel lithography technique.