Micro-fluidic actuation using magnetic artificial cilia

Abstract

We demonstrate advanced fluid manipulations using magnetic polymeric artificial cilia on the walls of a microfluidic channel. In nature, cilia are little hairs covering the surface of micro-organisms which enable them to manipulate a fluid on the micro-scale. The asymmetric movement of natural cilia is crucial to obtain a net fluid flow. We have developed a ferromagnetic polymer made from iron nanoparticles and polydimethylsiloxane, and describe a process that can structure the material into high aspect ratio lying artificial cilia with a length of 300 µm. These artificial cilia were actuated with a homogeneous rotating magnetic field (µ₀H < 50 mT) generated with a compact external electromagnet. An asymmetric movement involving torsion could be created when the cilia were provided with a remanent magnetisation perpendicular to the plane of rotation of the magnetic field vector. The artificial cilia could be actuated in fluid up to a frequency of ∼50 Hz. In an aqueous solution in a microfluidic chamber we were able to generate rotational as well as translational fluid movements with fluid velocities up to ∼0.5 mm s⁻¹.