Artificial cilia: mimicking nature through magnetic actuation
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Artificial cilia: mimicking nature through magnetic actuation S. N. Khaderi1, M. G. H. M. Baltussen2, P. D. Anderson2, D. Ioan3, J. M. J. den Toonder2 and P. R. Onck1 1 Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands 2 Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven, The Netherlands 3 Politehnica University of Bucharest, Spl. Independentei 313, 77206 Bucharest, Romania ABSTRACT Manipulation of bio-fluids in microchannels faces many challenges in the development of lab-on-a-chip devices. We propose magnetically actuated artificial cilia which can propel fluids in microchannels. These cilia are magnetic films which can be actuated by an external magnetic field, leading to an asymmetric motion like that of natural cilia. The coupling between different physical mechanisms (magnetostatics, solid mechanics and fluid dynamics) is numerically established. In this work we quantify the flow through a microfluidic channel as a function of its geometry for a characteristic set of dimensionless parameters. INTRODUCTION Manipulation of bio-fluids in microchannels finds very interesting applications in medical diagnostics. For example, in lab-on-a-chip devices a bio-fluid which is to be analyzed has to pass through several stages, such as mixing (with a catalyst), incubation (during which reactions take place over precise time periods) and detection of biomolecules. The search for new ways of propelling the bio-fluid through these stages is a very active field of research [1]. One of the characteristics of fluid flow at the micron scale is that the viscous forces are dominant over the inertial forces so that the latter can be considered negligible. A consequence of this is that the movement of the actuator should be asymmetric [2] in order for the fluid to be propelled. Such actuators can be found in nature (i.e. hair-like structures known as cilia) which enable micro organisms, such as paramecia, to swim. Recently we have demonstrated that magnetic artificial cilia, actuated by an external magnetic field, are able to propel fluids in microchannels [3]. In this work [3], the natural cilia are mimicked by polymer films with embedded nanoparticles which can be actuated by a tuned external magnetic field to exhibit an asymmetric motion. Two configurations were proposed: a permanently magnetic film (PM) subjected to a sudden magnetic field and a super-paramagnetic film (SPM) under the influence of a rotating external magnetic field. It was shown that the flow through a microfluidic channel is proportional to the area swept by the film, and we explored the dependence of the swept area on the ciliated-system parameters (film length and thickness, mechanical and magnetic film properties and the applied field) for one specific channel geometry. In this paper, however, we fix the parameters of the cilia system and explore the effect of the channel geometry (cilia spacing and height) on the induced fluid flow.
METHOD We study a periodic ar
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