Precise Detection of the Droplet Size for Droplet Microfluidics

The electrical-detection method for precise detection of the droplet size is demonstrated in this paper. For the T -junction microdroplet generator, three pairs of the microelectrodes are allocated along the microchannel, and during the passing-by process of each droplet, both the length and the velocity of the droplets can be obtained by measuring the time-varying capacitance between each pair of the microelectrodes. Particularly, the mathematical model of the droplet microfluidic electrical-detection device is validated experimentally over a wide range of the droplet velocity, the droplet size and the microchannel geometries. By comparing the droplet size measured by the electrical-detection method with that by the method of image processing, the detection precision of the droplet size is verified experimentally. Most importantly, by calculating the root-mean-square value of the droplet lengths tested by three pairs of the microelectrodes, the detection precision of the droplet size can be increased drastically.