Generating ultra-small droplets based on a double-orifice technique

Generating individual, small droplets offers unique possibilities for various applications where precise volume and concentration control are necessary. This paper presents a systematic method for generating ultra-small droplets based on a controllable meniscus break-up procedure. The method utilizes two nozzles that are connected to a computer-controlled syringe through a three-way junction. A syringe is used to extrude the liquid from both orifices until they are connected by a liquid meniscus. Next, draining the liquid out of the meniscus and back into the nozzle will cause the meniscus to thin, which will ultimately result in its break-up and the formation of one small droplet. Both experimental and theoretical studies are presented to demonstrate the validity of the proposed method. It is shown that droplets with volumes from femtoliters to nanoliters can be generated. (C) 2017 Elsevier B.V. All rights reserved.