Performance optimization of droplet formation and break up within a microfluidic device – Numerical and experimental evaluation

[Display omitted] •It is observed that mineral oil with lower surface tension produces the most stable and round droplets comparing to the two other oils.•for a constant Capillary number, the size of droplets decrease due to decrease in flow rate ratio in a specific oil.•By increasing the Capillary number, which can be stated as the predominance of viscous forces, the formation of droplets with larger sizes in the form of plugs occurs.•To characterize the parameters affecting the size of droplets and consider the effect of the two-phase flow ratio on the dynamics of droplet formation and Capillary number of the continuous phase, a model has been proposed for estimating the droplet size of three types of oils used in the experiment.•The study of the effects of the type of oil on the frequency of droplet formation and the distance between droplets showed that the rate of droplet formation in mineral oil has the lowest amount which is followed by paraffin oil and olive oil, respectively. The highest distance between droplets is observed in mineral oil, followed by oils including paraffin and olive, respectively.•With the increase in the Capillary number (the ratio of viscous forces to surface tension), in the ratio of constant flow rate, the frequency of droplet formation increases, and the distance between droplets decreases. Droplet-based microfluidics, including the controlled manipulation of materials in the form of monodisperse droplets on the micrometer scale in microfluidic chips, has gained much attention due to their ability in biological assays. The capillary number of the continuous phase, as the ratio of viscous force and interfacial tension, is so important in the mechanism of droplet formation. This study aims to survey the type of continuous-phase fluid, the change in the parameters of the continuous phase, and the effect of the different flow rates ratios on the droplet formation dynamics, droplet size, distance between droplets and frequency of droplet formation. Three types of oil, including mineral, olive, and paraffin in a flow-focusing microfluidic device have been utilized numerically and experimentally. To characterize the parameters of the continuous phase affecting the droplet size, a microfluidic device has been designed to estimate of the droplet size for three different types of oil used in the assay. The results show that for a constant continuous phase velocity, the diameter of the droplets formed in olive oil has the lowest amou