MODELING MULTI-COMPONENT FLUID-STRUCTURE INTERACTION AT THE MICROSCALE

<p dir="ltr">Multi-component Fluid-Structure Interaction (MCFS) at micro-scale is a phenomenon in which capillary forces at fluid-fluid interfaces drive the solid’s deformation. MCFS plays an important role in many micro- and nano-scale applications, including inkjet printing, microfabrication, and microfluidics. Although previous studies have addressed several notable MCFS problems, limited attention has been given to systems involving many immiscible fluid components, high flow rates, and advanced nonlinear solid materials. This lack of attention is because of limited available computational tools available for accurately modeling and understanding such problems. To address this research gap, we accomplish two primary research objectives. First, we develop a computational MCFS model that can handle systems involving a nonlinear solid and three immiscible fluids. Our model employs the phase-field method and defines a fluid-solid surface energy function to control wettability, and the tractions transmitted to the solid at the fluid-solid interface. We employ a boundary-fitted approach for our FSI formulation and use Isogeometric Analysis for the spatial discretization. We validate our computational model against experimental results and assess its performance through simulations of compound droplet-solid interaction. To accomplish our second objective, we use our model to better understand three new fundamental mechanisms in MCFS: a) we propose a novel gradient-free and spontaneous droplet transport mechanism, termed fibrotaxis, on deformable anisotropic solids; b) we observe that tube’s deformability delays or suppresses the onset of interfacial instabilities in capillary tubes; c) we demonstrate that actuating deformable constricted tubes at their resonant frequency enables significantly faster droplet transport. Our model and our innovative computational framework advances the field of computational fluid dynamics, and contributes significantly to the advancement of technologies in microfluidics, lab-on-chip devices, microfabrication, and self-cleaning surfaces.</p>