Nature-inspired microfluidic propulsion using magnetic artificial cilia

Abstract

Lab-on-a-chip is a technology that aims at performing analyses of biological samples (such as blood and urine), conventionally performed in a clinical lab, on a small chip. The lab-on-a-chip consists of micro-chambers (where dedicated tests are carried out) connected by micro-channels, through which the bio-fluid has to pass through. In this work, we explore a way to propel fluids through these micro-channels by mimicking the fluid transport mechanisms present in nature at small length scales. Micron-scale fluid propulsion takes place in nature using hair-like motile appendages known as cilia that beat out-of-phase to result in a wave-like motion (metachronal waves). In addition, individual cilia beat in an asymmetric manner with a distinct effective and recovery stroke. During the effective stroke the cilia are straight and push a large amount of fluid, whereas during the recovery stroke they stay closer to the cell surface and pull back a small amount of fluid. The net fluid propelled is in the direction of the effective stroke. In this work we design artificial cilia that can be realized using thin films consisting of a polymer matrix filled with magnetic nano-particles, so that they can be actuated using an external magnetic field. We use a coupled magneto-mechanical solid-fluid numerical model to find under what conditions a magnetic film will mimic the asymmetric motion of natural cilia. The response of the artificial cilia is further studied in terms of the dimensionless parameters that govern their physical behavior and the parameter space in which the cilia can generate maximum flow is identified.