Easily fabricated monolithic fluoropolymer chips for sensitive long-term absorbance measurement in droplet microfluidics

Maintaining a hydrophobic channel surface is critical to ensuring long-term stable flow in droplet microfluidics. Monolithic fluoropolymer chips ensure robust and reliable droplet flow as their native fluorous surfaces naturally preferentially wet fluorocarbon oils and do not deteriorate over time. Their fabrication, however, typically requires expensive heated hydraulic presses that make them inaccessible to many laboratories. Here we describe a method for micropatterning and bonding monolithic fluoropolymer flow cells from a commercially available melt-processable fluoropolymer, Dyneon THV 500GZ, that only requires a standard laboratory oven. Using this technique, we demonstrate the formation of complex microstructures, specifically the fabrication of sensitive absorbance flow cells for probing droplets in flow, featuring path lengths up to 10 mm. The native fluorous channel surface means the flow cells can be operated over extended periods, demonstrated by running droplets continuously through a chip for 16 weeks.