Magnetic Flux Concentrator

Introduction

When a permanent magnet is used for capturing magnetically labeled pathogens in microfluidic channels in diagnostic applications, pronounced peaks of magnetic field around the magnet edges result in accumulation of piles of beads in those areas obscuring the pathogen detection.

Shaping magnets, such as rare earth magnets to address the problem is not practical due to health hazards and technical issues such as machinability. A better solution is to use a magnetic flux concentrator fabricated from a well-machinable nickel-iron magnetic alloy and wrapping around the permanent magnet. [pdf]

• ~ 19 x 19 x 19 mm neodymium magnet

• EFI alloy 79 magnetic alloy

• 400 x 400-micron slits

Calculated magnetic field gradient in the microfluidic channel in configuration with magnet only and with magnet combined with magnetic flux concentrator (MFC)

Photographs of magnetically captured beads in the absence or presence of magnetic flux concentrator