Superparamagnetic particle dynamics and mixing in a rotating capillary tube with a stationary magnetic field

• Published in: Microfluidics and nanofluidics Vol. 13; no. 3; pp. 461 - 468
• Main Authors: Lee, Jun-Tae, Abid, Aamir, Cheung, Ka Ho, Sudheendra, L., Kennedy, Ian M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.09.2012; Springer; Springer Nature B.V
• Subjects: Analytical Chemistry; Applied fluid mechanics; Bioassays; Biological and medical sciences; Biomedical Engineering and Bioengineering; Biosensors; Biotechnology; Chemical reactions; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Diamagnetism, paramagnetism and superparamagnetism; Dynamics; Engineering; Engineering Fluid Dynamics; Exact sciences and technology; Fluid dynamics; Fluid flow; Fluidics; Fundamental and applied biological sciences. Psychology; Fundamental areas of phenomenology (including applications); Magnetic fields; Magnetic properties and materials; Methods. Procedures. Technologies; Nanostructure; Nanotechnology and Microengineering; Physics; Research Paper; Rotating; Various methods and equipments; Viscosity; Viscous drag; Magnetic particles; Mason number; Rotating capillary; Particle chains; Mixing; Superparamagnetism; Particle suspension; Experimental study; Capillary tube; Rotating pipe; Biosensors; Magnetic fields; Microstructure; Microfluidics
• ISSN: 1613-4982; 1613-4990
• DOI: 10.1007/s10404-012-0981-z

The dynamics of superparamagnetic particles subject to competing magnetic and viscous drag forces have been examined with a uniform, stationary, external magnetic field. In this approach, competing drag and magnetic forces were created in a fluid suspension of superparamagnetic particles that was confined in a capillary tube; competing viscous drag and magnetic forces were established by rotating the tube. A critical Mason number was determined for conditions under which the rotation of the capillary prevents the formation of chains from individual particles. The statistics of chain length was investigated by image analysis while varying parameters such as the rotation speed and the viscosity of the liquid. The measurements showed that the rate of particle chain formation was decreased with increased viscosity and rotation speed; the particle dynamics could be quantified by the same dimensionless Mason number that has been demonstrated for rotating magnetic fields. The potential for enhancement of mixing in a bioassay was assessed using a fast chemical reaction that was diffusion-limited. Reducing the Mason number below the critical value, so that chains were formed in the fluid, gave rise to a modest improvement in the time to completion of the reaction.