Nature-inspired micro-fluidic manipulation using artificial cilia

1. Nature-inspired micro-fluidic manipulation using artificial cilia Philips Corporate Technologies, IMTEK, Liquids Research Ltd., University of Groningen, Politehnica University of Bucharest, University of Bath, Delft University of Technology, Eindhoven University of Technology jaap.den.toonder@philips.com Cilia The experimental set-up Micro-organisms such as Paramecium use tiny beating micro-hairs, “cilia”, with which their surface is covered, to propel themselves through a liquid. Cilia have a typical length of 10 m and beat asymmetrically. Inspired by this, we have developed “artificial cilia”: polymer composite micro-actuators responding to an applied magnetic field. A possible application is the manipulation of fluids in microfluidic lab-on-chip devices. To test the pumping effectiveness of our artificial cilia, we developed a microfluidic cartridge in which the cilia were integrated on the floor of a microchannel. The cartridge was placed in the heart of a magnetic actuation system, which was either a set of individually addressable magnetic poles, or a rotating permanent magnet, to produce a time-varying magnetic field for cilia actuation. Artificial cilia Particle Image Velocimetry Experiments Our artificial cilia, made with a specially developed two-color lithography process, are thin rubber (PnBA) flaps containing dispersed super paramagnetic nanoparticles (Fe3O4). They are typically 50 to 100 m long and 10 to 20 m wide, and are The flow generated by the artificial cilia in the microchannel was characterized quantitatively using micro Particle Image Velocimetry (PIV). The fluid (water) was seeded with micron-sized buoyant fluorescent particles. By the analysis of particle images taken as a function of time, time resolved velocities of the flow field over the cilia were obtained. anchored to the substrate at one end. The artificial cilia are sufficiently compliant and magnetic to be actuated with a magnetic field that can be generated by a permanent magnet or an electromagnet. Simulations of the induced flow velocity From the PIV measurements, the averaged velocity distribution over the channel height was determined. Average velocities of up to hundreds of m/s were found. This corresponds to flow rates of around 20 l/min in a channel with a mm-sized cross section. We have developed numerical models capable of simulating the flow induced by the actuated cilia, including the full interaction between the elastic cilia and the, possibly complex, fluid. Results show that, by using special magnetic actuation protocols, the cilia can be made to move asymmetrically as in nature, and generate a net flow. An out-of-phase motion of neighboring cilia, resulting in a metachronic wave, can enhance the effect. The models predicts flow rates of over 10 l/min in a typical microfluidic channel. Conclusion Our magnetic artificial cilia can generate a flow of tens of l/min in microchannels. This is comparable with other microfluidic pumps. Advantages of our approach are that it offers local control, does not require external connections, and is compatible with bio-fluids.