Self-Similar Relaxation of Confined Microfluidic Droplets

Margaux Kerdraon (1) , Joshua D Mcgraw (2) , Benjamin Dollet (3) , Marie-Caroline Jullien (2, 4)

1 LPCT - Laboratoire de Physico-Chimie Théorique
2 MMN - Laboratoire Microfluidique, MEMS, Nanostructures
3 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]
4 IPR - Institut de Physique de Rennes

We report an experimental study concerning the capillary relaxation of a confined liquid droplet in a microscopic channel with rectangular cross-section. The confinement leads to a droplet that is extended along the direction normal to the cross-section. These droplets, found in numerous microfluidic applications, are pinched into a peanut-like shape thanks to a localized, reversible deformation of the channel. Once the channel deformation is released, the droplet relaxes back to a plug-like shape. During this relaxation, the liquid contained in the central pocket drains towards the extremities of the droplet. Modeling such visco-capillary droplet relaxation requires considering the problem as 3D due to confinement. This 3D consideration yields a scaling model incorporating dominant dissipation within the droplet menisci. As such, the self-similar droplet dynamics is fully captured.

Domains: Physics [physics]

Margaux Kerdraon, Joshua D Mcgraw, Benjamin Dollet, Marie-Caroline Jullien. Self-Similar Relaxation of Confined Microfluidic Droplets. Physical Review Letters, 2019, 123 (2), ⟨10.1103/PhysRevLett.123.024501⟩. ⟨hal-02278038⟩