Fluoropolymer surface coatings to control droplets in microfluidic devices

Area of Science:

• Microfluidics
• Surface Chemistry
• Polymer Science

Background:

• Poly(dimethylsiloxane) (PDMS) is widely used in microfluidic devices.
• Controlling droplet behavior in microchannels is crucial for various applications.
• Surface modification of PDMS is essential for enhanced droplet manipulation.

Purpose of the Study:

• To apply low surface energy fluoropolymer coatings onto PDMS microfluidic devices.
• To investigate the effect of these coatings on droplet formation and merging.
• To develop a method for controlled droplet merging using extraction.

Main Methods:

• Initiated chemical vapor deposition (iCVD) was used to pattern fluoropolymer coatings.
• Coating was applied within microchannels based on geometrical constraints.
• Two-phase flow systems were utilized to study droplet dynamics.

Main Results:

• Fluoropolymer coatings significantly enhanced the range of accessible flow rates for droplet formation.
• Controlled coating at the inlet enabled a novel method for merging droplets.
• Extraction-induced droplet merging was achieved, with merging time dependent on organic spacer droplet size and flow rate.
• Droplet merging process was independent of the sizes of the droplets being merged.

Conclusions:

• Low surface energy fluoropolymer coatings improve droplet formation and manipulation in PDMS microfluidics.
• Extraction-induced droplet merging is a robust technique for controlling droplet interactions.
• This method holds potential for translating multi-step reactions to microfluidic platforms.