Electroosmotic flow in a poly(dimethylsiloxane) channel does not depend on percent curing agent

Area of Science:

• Materials Science
• Microfluidics
• Surface Chemistry

Background:

• Poly(dimethylsiloxane) (PDMS) is widely used in microfluidic devices.
• Electroosmotic flow (EOF) is a critical phenomenon in microfluidic applications.
• Controlling surface properties of PDMS is essential for predictable fluid behavior.

Purpose of the Study:

• To investigate the impact of the curing agent to base ratio in PDMS formulations on electroosmotic flow (EOF).
• To develop a novel method for permanently sealing PDMS microfluidic channels.
• To analyze the surface charge characteristics of PDMS-coated capillaries.

Main Methods:

• Fabrication of PDMS microfluidic devices using varying ratios of curing agent (silicon hydride groups) to base (vinyl-terminated PDMS).
• Development of a new technique for permanently enclosing PDMS microfluidic channels.
• Coating the inner walls of capillaries with PDMS prepared from different curing agent to base ratios.

Main Results:

• Electroosmotic flow (EOF) remained constant across all tested PDMS formulations, regardless of the curing agent to base ratio.
• The novel channel enclosure method proved effective for PDMS microfluidic device fabrication.
• Surface charge analysis indicated that negative charges are not solely derived from base or curing agent components.

Conclusions:

• The ratio of curing agent to base in PDMS does not influence the electroosmotic flow (EOF).
• The observed negative surface charges in PDMS are likely due to other factors not present in isolation in the base or curing agent.
• The study provides insights into PDMS surface chemistry relevant for microfluidic device design and optimization.