Rectifying jet breakup by electric forcing. Issue 2 (14th March 2023)

• Record Type: Journal Article
• Authors: Van Assche, David; Beneyton, Thomas; Baret, Jean‐Christophe
• Is Part Of: Droplet. Volume 2:Issue 2(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-03-14
• Subjects: Drops; Bubbles; Fluid mechanics; Periodicals; 530.427
• DOI: 10.1002/dro2.45
• Languages: English
• ISSNs: 2731-4375

Abstract

Abstract: The high‐throughput production of monodisperse droplets is paramount in most of the applications in droplet microfluidics. In a flow‐focusing junction, a straightforward way to increase droplet production rate is to increase the flow rates. However, at a critical flow velocity, the droplet monodispersity breaks down due to a transition from the dripping to the jetting regime. As a result, a much more polydisperse droplet population is generated. The change from monodisperse to polydisperse droplet production emerges from the intrinsic properties of the instabilities of jets. In the jetting regime, droplet pinch‐off is governed by a convective instability which amplifies random noise when traveling down the jet leading to an irregular breakup. We show that with the use of an amplitude‐modulated electric signal, we select the breakup frequency of the jet. Matching the perturbation frequency close to the natural breakup frequency of the jet, we increase the monodispersity of the droplet population. This method is applicable to droplet production at a high throughput, that is, beyond the dripping to jetting threshold, including an active control since the frequency, and hence droplet sizes, are determined by the forcing frequency. Abstract : The dripping‐to‐jetting transition limits the production of monodisperse droplets in a flow‐focusing junction: A jet is sensitive to external noise resulting in uncontrolled droplet production and drops of various sizes. We show that electric fields provide a means to apply locally controlled disturbances to rectify jets and increase the production rates of monodisperse emulsions. Our results are, therefore, relevant to the wide range of applications requiring ultrahigh‐throughput production of monodisperse microcompartments.