Regulation of microfluidic droplet generation by cyclodextrin-essential oil inclusion interactions

Based on the inclusion interaction between cyclodextrin and essential oil, we prepared oil-in-water type emulsion droplets using microfluidic technology. By changing the flow ratio of the continuous phase and the dispersed phase, and the types of cyclodextrin （α-CD, β-CD） and essential oils （cinnamon oil, mint oil）, we investigate their influence on the flow transitions and droplet generation. The experimental results show that as the flow ratio increases, the system undergoes a flow type transformation from dripping, jetting to threading. Compared with α-CD, β-CD forms a denser interfacial film with essential oils, which effectively reduces interfacial disturbances during shear deformation. As a result, we can produce monodisperse droplets across a wider operating range. Based on the above results, we propose that the mechanical strength of the interfacial film is a key parameter that determines the size of the droplets. Combined with the flow ratio, viscosity ratio and capillary number, a unified scaling law is used to predict droplet size. We provide a new strategy for regulating emulsion interfaces and construct droplet micro-reactors from the difference in supermolecular binding sites.