Easy-to-operate fabrication of tapered glass capillaries for microdroplet generations

摘要： Tapered glass capillaries play an important role in micro droplets generation and related micro?uidic applications such as particle synthesis, digital PCR, microrectors. However, its controlled production poses a challenge. Speci?cally, there is di?culty controlling the tip sizes of capillaries with good repeatability at an a?ordable cost, which is critical to producing standard droplets for use by research groups. To produce tapered capillaries, micro needle geometries are ?rst pulled by commercial pipette puller, which yields a sharp tip (i.e. 1-3μm). Those tips need to be enlarged and standardized by post microfabrication. Although larger tips could be achieved by advanced pulling-forging, sanding-forging or breaking-forging methods, the uniformity and repeatability do not meet the requirements for mass production. In this paper, several easy-to-operate fabrication approaches, including mechanical and chemical fabrication methods, are studied. Chemical etching fabrication method shows good repeatability and robust control of dimensions. A capillary droplet micro?uidic device assembled by tapered glass capillaries fabricated by chemical etching method is also presented, which shows good performance for droplet generations. This non-labor intensive fabrication is straightforward and be readily adopted for industrial scale mass production.