A New Silicon Mold Process for Polydimethylsiloxane Microchannels.

Area of Science:

• Materials Science
• Microfluidics
• Nanotechnology

Background:

• Traditional SU-8 soft lithography for polydimethylsiloxane (PDMS) microchannel fabrication presents limitations.
• Developing alternative, efficient, and maskless methods for microfluidic chip fabrication is crucial for advancing micro-scale applications.

Purpose of the Study:

• To propose and demonstrate a new silicon mold fabrication process for PDMS microchannel chips.
• To offer an alternative to conventional SU-8 soft lithography, utilizing picosecond laser technology.

Main Methods:

• A picosecond laser was employed to pattern a 550 μm thick silicon wafer, achieving a minimum feature size of 50 μm.
• Post-laser processing involved trimming edge debris with potassium hydroxide (KOH) and removing the field oxide layer with buffered oxide etch (BOE).
• Anodic bonding was utilized to secure the patterned silicon mold cores onto Pyrex 7740 or Eagle XG glass substrates.

Main Results:

• Successfully fabricated four-inch silicon wafers with microchannel patterns serving as PDMS mold cores.
• Demonstrated the feasibility of the maskless process for subsequent PDMS molding and demolding.
• A PDMS microchannel chip for particle separation was successfully produced as a proof-of-concept.

Conclusions:

• The proposed silicon mold process, utilizing picosecond laser cutting and anodic bonding, provides a viable maskless alternative for PDMS microchannel chip fabrication.
• This method eliminates the need for photolithography facilities, although it requires external laser cutting services.
• The technique is suitable for producing microfluidic devices, such as those used for particle separation.