Magnetically Actuated Beating Cilia for Pre-Concentration of Bacteria

Abstract

Detecting low concentrations of bacteria in food samples is a challenge. The pre-concentration and separation of the target bacteria from the food matrix can be enhanced using improved fluid handling. We have demonstrated a method for pre-concentration of bacteria from a liquid sample making use of arrays of artificial cilia. The cilia are defined using thin film processes on a glass substrate and are actuated magnetically with an external magnetic field. We demonstrate particle capture with cilia, by functionalizing the surface of the cilia with streptavidin protein and capturing biotin labelled particles on its surface. The functionalized cilia are incorporated inside a microchannel and biotin labelled particles are introduced into array of the cilia. The oscillating cilia are also capable of creating a net fluid flow which can be used for fluid pumping and mixing. We study the kinematics of the elastic cilia, with their asymmetric stroke, and demonstrate that it depends on two dimensionless numbers. To demonstrate pumping effects with arrays of cilia, we incorporate them on the inner walls of microchannel loop and measure the pumping rate while varying many of the parameters of the system. We report high pumping rates and characterize the fluid handling capability of such systems in terms of two dimensionless parameters.