A method to obtain uniform magnetic-field energy density gradient distribution using discrete pole pieces for a microelectromechanical-system- based magnetic cell separator

Abstract

A spatially uniform magnetic energy density gradient (∇ B2) distribution offers a controlled environment to separate magnetically tagged cells or biomolecules based on their magnetophoretic mobility [L. R. Moore, J. Biochem. Biophys. Methods 37, 11 (1998)]. A design to obtain a uniform ∇ B2 distribution for a microelectromechanical-systems-based magnetic cell separator was developed. The design consists of an external magnetic circuit and a microfabricated channel (biochip) with embedded discrete pole pieces on the channel walls. The two-dimensional and three-dimensional magnetostatic simulation softwares utilizing boundary element methods were used to optimize the positions and the dimensions of the discrete pole pieces, as well as the external magnetic circuit-the combination of which would generate a uniform ∇ B2 profile over the channel cross section. It was found that the discrete pole pieces required specific magnetic properties (saturation magnetization constant 1.55 T) to affect the overall ∇ B2 distribution. Investigating different positions of the discrete pole pieces inside the external magnetic field indicated that the proposed design could generate uniform ∇ B2 distribution with ±100 μm displacements along the height/width and ±1° inclination from the optimum position. © 2006 American Institute of Physics.