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Why some magnetic beads separate fast and others slow?

Latest theoretical investigations conducted by researchers from the Institut de Ciencia de Materials de Barcelona and the Grup de Fisica Estadistica de la Universitat Autonoma de Barcelona have shed some light on the key aspects of the magnetophoretic separation process.

separation magnetic particlesThe work of  Dr. Jordi Faraudo, Dr. Juan Camacho and Jordi Andreu show the existence of two different magnetophoretic regimes: a fast separation regime, where particles aggregate into clusters (cooperative magnetophoresis), and a slow one where particles do not aggregate (non-cooperative magnetophoresis). The magnetophoretic regime solely depends on the concentration, and the size and magnetic content of the particles in a well defined quantitative way. This fact provides a fast and reliable way to distinguish between fast (cooperative) and slow (non-cooperative) magnetophoretic separation regimes. These findings can help to design magnetic beads and Magnetic Bead Separation systems with faster separation times.

The theory has been tested with the experimental results of several magnetic beads and particles, mainly produced adhoc  by Dr. Maria Benelmekki at the Centro de Fisica of the Universidade do Minho (Braga, Portugal). The experimental work has been done in cooperation with Sepmag researchers, using precision magnetophoresis systems and the QCR monitoring add-on.

The researchers have also presented an analytical model to describe the kinetics of the separation process of superparamagnetic dispersions under homogeneous magnetic fields in the non-cooperative case. This analytical model has been possible due to the homogeneous and completely reproducible Magnetic Bead Separation conditions inside a Sepmag.


J. Andreu, J. Camacho, J. Faraudo. Aggregation of superparamagnetic colloids in magnetic fields: the quest for the equilibrium state. Soft Matter 7, 2336 (2011).

J. Andreu, J. Camacho, J. Faraudo, M. Benelmekki, C. Rebollo, Ll.M. Martinez. Simple analytical model for the magnetophoretic separation of superparamagnetic dispersions in a uniform magnetic field. Phys. Rev. E 84,  021402 (2011).

Lluis M. Martínez | SEPMAG Chief Scientific Officer

Founder of SEPMAG, Lluis holds a PhD in Magnetic Materials by the UAB. He has conducted research at German and Spanish academic institutions. Having worked in companies in Ireland, USA and Spain, he has more than 20 years of experience applying magnetic materials and sensors to industrial products and processes. He has filed several international patents on the field and co-authored more than 20 scientific papers, most of them on the subject of magnetic particle movement.

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