Liquid flow mode transition and hysteresis under passive control

The liquid flow mode exerts a significant influence on the dynamics of droplet breaking, with consequential effects on factors like droplet size and monodispersity. In various applications, including but not limited to inkjet printing, microcapsule preparation, and cell encapsulation, diverse production methods are employed, but they typically rely on some form of droplet breakup or liquid jet breakup to ultimately generate droplets. During the process of droplet formation, smaller satellite droplets, which are considerably smaller than the main droplet, are inevitably generated. These smaller droplets can lead to wastage of raw materials and reduced production efficiency. Passive control methods, which involve modifications to the structure of the dropper, effectively suppress the formation of satellite droplets, and prove to be more practical and manageable in actual production scenarios when compared to active control methods. In contrast to the jetting mode, the dripping mode of droplet molding exhibits greater stability and size uniformity, thereby better meeting the requirements for particle uniformity in the preparation of traditional Chinese medicine. This paper specifically investigated the transition from the jetting mode to the dripping mode and explored the hysteresis of this transition under the influence of gravity utilizing a passive control method. By incorporating a drainage device within the dropper along with a Y-channel, a drainage system was established to achieve passive control. The effects of the length and diameter of the drainage device, as well as the mass fraction of the solution, on the conversion of flow modes were analyzed.