An on-chip magnetic bead separator using spiral electromagnets with semi-encapsulated permalloy

A new planar bio-magnetic bead separator on a glass chip has been designed, fabricated and tested. The separator is composed of micromachined semi-encapsulated spiral electromagnets and fluid channels, which have been separately fabricated and then bonded. The device was tested with super-paramagnetic beads of mean diameter 1 mum which were suspended in a buffered solution. When a DC current of 300 mA was applied to the inductor, the bio-magnetic beads were successfully separated on the electromagnets, showing a functional capability as a magnetic bead separator. To evaluate separation rate and capability, the inductance measurement method has been introduced and the inductance variation according to the separation rate has been characterized. Using this separator, cells or cell fragments and magnetic beads bonded with protein or enzyme suspended in bio-buffer solutions can be successfully separated from their suspensions, envisaging a filterless bio-separator. (C) 2001 Elsevier Science BY. All rights reserved.