Generation of water–ionic liquid droplet pairs in soybean oil on microfluidic chip

Droplet-based microfluidic chips have shown great advantages in fields of chemical and biological researches. Based on the different wettabilities of water, IL (ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate) and soybean oil in hydrophobic channels, three kinds of droplet pairs (including an alternating water–IL droplet chain, connected water–IL droplet pairs and separated water–IL droplet pairs) were generated for the first time in soybean oil on microfluidic chips containing double flow-focusing regions. The influences of fluid flow rate and channel geometry on droplet pair formation were carefully studied.