Custom Magnet Design for a Multi-Channel Magnetic Microcytometer

Magnetic microflow cytometers integrate magnetic field sensors and microfluidic channels to detect cell suspensions labeled with magnetic beads. As the magnetic beads are superparamagnetic, commercial permanent magnets (PMs) are typiacally positioned bellow the microchip for an out-of-plane magnetization. Though, they require careful alignment as their magnetic field can impact the sensors sensitivity. In this paper, we overcome this drawback by presenting an innovative custom-made PM that notably combines high out-of-plane magnetic field (>100 mT) and low in-plane magnetic field (<;1mT) over a large area (30.2mm
²
). This configuration qualifies the setup for simultaneous detection in multiple microfluidic channels within the same microchip, allowing parallel analysis of different cell samples or faster analysis of larger volumes of cell suspension.