Sliding mode control of droplet size in a microchannel by adjusting syringe-pump flow: Experimental study

Microfluidics has many applications in modern sciences such as medicine and biomedical engineering. There are usually two ways of injecting fluids; using pressure regulations in fluid flow lines and using syringe pumps, which using syringe pumps is the most common way. Today, a lot of research has been done in this field, but a limited number of them have focused on active control of the droplet size. In this research, a microchannel was first fabricated using photolithography. To inject fluids into the channels, a syringe pump is designed and built using a DC motor with suitable speed and torque and the L298N module. The fluids used in this research are double distilled water as a discrete phase and oil as a continuous phase. An Arduino Mega 2560 board has also been used as the processor to automatically control this system. The droplet diameter is calculated using a digital microscope and its image processing with a high-speed algorithm. The sliding mode control algorithm has been used to control the droplet size due to the nonlinearity of the system behavior as well as the disturbances. The obtained results for three different diameters i.e. 82, 90, and 100 µm, show the accurate performance of the sliding mode controller.