In this work, a novel structure, high-aspect-ratio-induced (HIDS) structure, is developed for the micro-droplet generation based on self-breakup mechanism. Comparing with the traditional microfluidic-based methods, there are two main advantages. Firstly, in HIDS only one input is required for driving the droplet generation process, and hence, the design and fabrication is much more concise and cheap. Secondly, the droplet size is insensitive to the flow rates so that it has a high turbulence tolerance, and hence, is suitable for large-scale parallelization. However, for a single HIDS channel the maximum generation frequency is limited at around 30 Hz because of the polyemulsion. Therefore, trenches are utilized to optimize this structure. Upon the careful design of the structures of tre...[ Read more ]

In this work, a novel structure, high-aspect-ratio-induced (HIDS) structure, is developed for the micro-droplet generation based on self-breakup mechanism. Comparing with the traditional microfluidic-based methods, there are two main advantages. Firstly, in HIDS only one input is required for driving the droplet generation process, and hence, the design and fabrication is much more concise and cheap. Secondly, the droplet size is insensitive to the flow rates so that it has a high turbulence tolerance, and hence, is suitable for large-scale parallelization. However, for a single HIDS channel the maximum generation frequency is limited at around 30 Hz because of the polyemulsion. Therefore, trenches are utilized to optimize this structure. Upon the careful design of the structures of trenches and leading rails, the inlet channel with high aspect ratio can successfully lead the dispersed phase into individual droplets at relatively high frequency. This ensures its excellent suitability in the applications like integrated microsystems. Volume fraction of the emulsion droplets in the continuous phase can also be controlled simply through the adjustment of the applied pressure on the continuous phase. A very high volume fraction can be achieved, which can save a large amount of continuous phase compared to the traditional methods like flow focusing. Experiments also show the droplets size still weakly depends on the flow rate even when it’s relatively high. It is also proved that structure with trenches owns a lower sensitivity of the droplet size to the flow rate, compared to that without trenches, which is a significant advantage to enhance the stability of droplets generation. The droplet formation process is simulated and it is found that the flow rate of the continuous phase around the trenches is extremely low, based on which we propose a geometric theoretical model. This model predicts the droplet size in a great agreement with our experimental data. I believe this generator can be widely applied in microfluidic systems, especially for the case of large-scale parallelization.