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Permanent magnets vs. Electromagnets: considerations for scaling up magnetic beads separation processes

Electromagnets are the classical way to generate intense magnetic fields. If you apply the electrical current across a coil, the magnetic field is quite small. But if you wrap the coils around an iron yoke, you can generate much stronger magnetic fields. Unfortunately, if you need to scale up a magnetic separation process, you also need to increase the electrical power to the magnetic separation rack and the amount of iron and copper used for the coil.

Download our Free Guide on Biomagnetic Separation Scale-up HERE.

This post is about Magnetic Bead Separation with a magnetic separation rack, and how to scale-up this process. If you are interested in this topic, download our free eBook The Basic Guide to Scale-up Magnetic Bead Separation Processes:

What happens when we use bigger magnets?

The heat generated by the resistance of the larger coils will be significantly greater as you scale up and will require a substantial electromagnet cooling system. Theoretically, you can adjust the values of the magnetic fields or change the field profiles that generate the magnetic force in Magnetic Bead Separation devices. However, once you produce large lots you will need to accurately control the electromagnet adjustable parameters (electrical current, pole pieces, system temperature).

In production facilities you will need to ensure you are always using exactly the magnetic separation conditions you have already validated. Therefore, when you scale up a magnetic separation system that uses an electromagnet, you must consider the additional cost of the following:

  • Much larger electric bill
  • Power supply maintenance (for a power supply compliant with the Electromagnetic compatibility of your lab)
  • Larger floor space
  • A refrigeration infrastructure able to flow enough water to control the temperature of your device
  • Maintenance of used coils, isolations, electronics and yoke.

MRIs typically use superconducting coils to avoid many of the above problems. However, for a system similar to an MRI, you will need to cryogenically cool the coils, making this technology far too expensive for a Magnetic Bead Separation device.

Rare Earth Permanent Magnets, the perfect solution

A better alternative to electromagnets is the use of Rare Earth Permanent Magnets to generate the required magnetic field profile. Homogeneous Magnetic Bead Separation systems can utilize these Rare Earth Magnets because the parameters of the separation process in these devices can be well defined (e.g. the optimal magnetic force and the field profile necessary to magnetically saturate the beads).

With Rare Earth Permanent Magnets, conditions comparable to those using Electromagnets can be achieved with less weight, no need for cooling systems, no electrical power, no power supply and no maintenance costs. If the device is used at temperatures less than 80ºC, conditions will remain constant for decades.

Therefore, Rare Earth Permanent Magnets provide a solution that gives you long term stability, a small footprint, and a one-time upfront cost for the system itself with no maintenance fees. Compared with Electromagnets, Rare Earth Permanent Magnets are a much more cost effective and reliable way to power Magnetic Bead Separation devices.

Don’t forget to check these posts from our blog in order to get a deeper insight into the scaling-up of Magnetic Bead Separation processes:

Check to access to FREE eBooks on the subject, or contact us. We will be glad to help you to achieve an efficient magnetic bead separation process!

magnetic separation rack

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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