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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 47: Wetting, Droplets, and Microfluidics (joint session DY/CPP)
CPP 47.9: Talk
Thursday, March 21, 2024, 17:15–17:30, BH-N 334
Active-matter-fueled interfacial microflows — •Kuntal Patel1,2 and Holger Stark1 — 1Institut für Theoretische Physik, Technische Universität Berlin, Berlin, Germany — 2Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
Several chemical and biomedical applications require systematic processing of micron-sized fluid samples. To realize this, so-called microfluidic lab-on-a-chip devices with micron-sized channels are widely used. Often, one needs to manipulate interfaces separating immiscible fluids in such channels. The interface separating the two fluid components costs energy, which is quantified by surface tension. Thus, any deformation of a planar fluid interface increases energy.
In our work, we assign one more property to the interface in the form of dipolar forces acting perpendicular to the interface. We name it the activity of the interface, and it is achieved by covering the interface with active particles. The notion of activity is inspired by swimming microorganisms. Using lattice-Boltzmann simulations, we discover that the presence of activity affects the stability of the interface. We notice that dipolar forces pointing towards the interface counter the stabilizing effect of surface tension, so that the interface deforms. In contrast, force components pointing away stabilize the planar interface. We demonstrate that one can leverage such activity-induced instability to generate microfluidic droplets and manipulate liquid sheets. In addition, we can also control droplet formation by varying the magnitude of dipolar forces in real time, which can be accomplished using light-sensitive active particles in practice.
Keywords: Microfluidics; Droplets; Active matter; Lattice-Boltzmann method; Phase field