Capture of micro- and nano-particles in high gradient magnetic field

Abstract

We investigate the capture of micro-particles by random wires in axial magnetic filters by using the expressions of high gradient magnetic field and fluid flow field around the wires previously determined, respectively, by using the effective medium treatment (EMT) and Happel, s cell model. We determine filter efficiency with the strength of applied magnetic field, the wire volume packing fraction in the filter and the fluid entrance velocity as parameters. We newly investigate diffusive capture of nano-particles by micro-wires implanted in blood vessel and compare the results with those obtained by considering only interception capture. Magnetic and fluid flow fields around each wire are determined analytically and numerically, respectively. We study the pattern of particle concentration distribution on a plane perpendicular to wire, s axis by solving the continuity equation numerically and using assigned initial and boundary conditions. The varied parameters are magnetic field strength, particle radius, and blood average velocity. From our results, the efficiency of micro-particle capture by axial filter determined by using the EMT model supports the previously reported experimental data. From this study, the basic criterion of the limitation of the single wire approximation is also provided. For results of nano-particle capture, particle concentration on the wire surface can be increased much higher than the injected value. The results imply the feasibility and the efficacy of using micro-wires for large scale blood separation and targeting nano-particles at specific sites within blood vessel.