CENTRIFUGO-MAGNETOPHORETIC SEPARATION AND ROUTING OF PARTICLES Jonathan Siegrist 1 , Laëtitia Zavattoni 1 , and Jens Ducrée 1,2 1 Biomedical Diagnostics Institute (BDI), National Centre for Sensor Research (NCSR), Dublin City University, Dublin, IRELAND 2 School of Physics, Dublin City University, Dublin, IRELAND ABSTRACT This paper reports on the manipulation of magnetic particles in a microfluidic environment through a novel, 2-dimensional particle separation combining centrifugal sedimentation with magnetic deflection. Operation in a centrifugally enabled, stopped-flow mode (i.e., no fluid flow, mere sedimentation) minimizes divergent flow lines and hydrodynamic instabilities that are typical in pressure- driven microfluidic set-ups [1]-[3]. Hence, our novel system excels with density, size, and magnetic-field dependent particle separation in a frequency-controlled, 2-dimensional force field. INTRODUCTION Background The integration of magnetic actuators with microfluidic chips has resulted in a surge of research output for both academia and industry [1][3]. The interplay between magnetic forces and the unique conditions found in microfluidic systems has generated many microscale engineering challenges, while the promise for real-world applications, for example in systems biology and diagnostics, remains strong, especially for separation applications (e.g., for concentration and purification of cells, proteins, or DNA). The development of a microfluidic separation system would have many applications, especially as related to biological cell-sorting. Design Concept In this work, a microfluidic, magnetophoretic system based on the earlier work by Pamme et al. [2] was adapted into a centrifugal-based system towards particle-assisted cell separation applications (Fig. 1). The compact-disc (CD) Figure 1: Schematic and photograph (inset) showing an overview of the centrifugal microfluidic device. based device works by centrifugally sedimenting particles in a stagnant carrier fluid through a permanent magnetic field. The entire system is first filled/primed with liquid, and then particles are introduced to the loading chamber (Fig. 2). After mounting of the permanent magnet onto the CD device, the CD is placed on a spin-stand motor and spun at various spin-speeds (revolutions-per-minute, RPM) to centrifugally sediment and separate the particles. The particles first enter the focusing channel where they are aligned along the distant wall with respect to the magnet. In the case of non-magnetic particles, the particles exit the focusing channel, pass on a straight, radial trajectory through the separation chamber, and then sediment directly into capture finger 1 farthest from the magnet (i.e., no magnetic deflection). For reference, the capture finger closest to the magnet is referred to in this work as capture finger 13, and the capture finger farthest from the magnet is referred to as capture finger 1. Figure 2: (A) Photograph showing the relevant features of each device (for reference, each capture finger is 170 µm wide), and (B) Schematic showing the experimental parameters that were varied: X and Y–spacing of the magnet from the capture fingers, M–permanent magnet properties, f C –centrifugal force (a function of CD spin-speed), P-particle properties (e.g., magnetic vs. non-magnetic), and D–particle diameter (particle not drawn to scale). 978-1-4244-9633-4/11/$26.00 ©2011 IEEE 1107 MEMS 2011, Cancun, MEXICO, January 23-27, 2011