Nanoscale surface modifications to control capillary flow characteristics in PMMA microfluidic devices

Area of Science:

• Materials Science
• Microfluidics Engineering
• Surface Chemistry

Background:

• Polymethylmethacrylate (PMMA) is a common material for microfluidic devices.
• Surface properties significantly influence fluid behavior in microchannels.
• Controlling surface energy and roughness is crucial for optimizing microfluidic performance.

Purpose of the Study:

• To investigate the impact of surface modifications on PMMA microfluidic devices.
• To analyze the effect of plasma treatment and diamond-like carbon (DLC) coatings on surface properties.
• To correlate surface characteristics with capillary flow dynamics and filling times.

Main Methods:

• Fabrication of PMMA microfluidic devices using hot embossing with integrated micro-pillars.
• Surface modification via plasma treatment and DLC film deposition.
• Measurement of static water contact angles to quantify surface energy changes.
• Analysis of capillary flow rates and microfluidic chamber filling times.

Main Results:

• Surface modifications resulted in significant changes in static water contact angles, ranging from 44.3° to 81.2°.
• Devices with lower static contact angles exhibited significantly faster fluid flow and reduced filling times.
• The presence of micro-pillars increased the filling time compared to devices without pillars.

Conclusions:

• Surface modification techniques effectively alter the surface energy of PMMA microfluidic devices.
• Lower surface energy, indicated by reduced contact angles, enhances capillary flow efficiency.
• Micro-pillar integration, while potentially useful for other functions, impedes capillary flow and increases filling times in these devices.