Precise detection of the low-quality cooking oil by monodisperse droplet generation in a flow-focusing microdroplet generator

Background: To precisely and efficiently detect the low-quality cooking oil is of great importance to guarantee the food safety in our daily life. Due to the complexity of its origin, the convenient and effective detection methods are still under research. Results: In a flow-focusing microdroplet generator, a new method is provided to detect the low-quality cooking oil based on droplet microfluidics. By controlling the driving pressure of the continuous and the disperse phase, monodisperse water-in-oil droplets can be formed in the flow-focusing microchannel. In particular, as the droplet size is varying with the fluid viscosity and the viscosity of the low-quality cooking oil is different from that of the high-quality cooking oil, therefore, various types of the edible oil samples can be distinguished by measuring the droplet size. Especially by using the method of image processing, the size of the droplets can be measured accurately in the flow-focusing microchannel, which can significantly improve the detection accuracy of the low-quality cooking oil. Significance: In particular, for a specific design of the flow-focusing microdroplet generator, this new method can also provide high reliability for the detection of the deep refined cooking oil based on droplet microfluidics.