Microdroplet Generation with Dilute Surfactant Concentration in a Modified T-Junction Device

Emulsions with very low surfactant concentration or without surfactant are highly required in many fields. Microfluidics have proven to be a promising emulsion preparation method. However, for the fresh interface formation during microfluidic droplet generation, excessive amounts of surfactant are also demanded to speed up surfactant transfer and drive low interfacial tensions. Here we present a newly designed capillary embedded T junction microdevice to intensify surfactant mass transfer for microdroplet generation. Within the device, surfactant molecules are concentrated onto the tip of the droplet breakup very fast by hydrodynamic forces, leading to extremely low dynamic IFTs temporarily. Microdroplets as small as 15 mu m are generated with surfactant concentrations significantly lower than their CMC values, when the concentrations of SDS, Tween 20, and F68 are only 0.05 wt % (1/6 CMC), 0.20 wt % (4/7 CMC), and 0.20 wt % (2/3 CMC) individually. The novel method would be promising in fields of biocompatible material, drug delivery, and food-grade microemulsions.