A Microfluidic Chip Utilizing Controllable Moving Walls for the Formation of Micro-droplets in Liquids

The formation of micro-scale droplets in liquids is crucial in the emulsification process, which is commonly used for a variety of industrial applications. This paper reports a new microfluidic chip capable of generating uniform micro-droplets in liquids for emulsification applications. The microfluidic chip can generate uniform micro-droplets utilizing a novel combination of hydrodynamic focusing and liquid-chopping techniques called a "controllable moving wall structure". Sample flow is first hydrodynamically focused into a narrow stream using neighboring sheath flows. A pair of side chambers placed orthogonal to the sample flow channel is then used to produce moving walls. By controlling the frequency of injected compressed air and the applied pressure to the side chambers, the pre-focused sample flow can be cut into micro-droplets with a uniform diameter. Experimental results show that micro-droplets with a diameter of tens of micrometers can be generated successfully by using the developed chip device. The micro-droplets have a much more uniform size when compared to previous studies. This new microfluidic device can be promising for emulsification applications