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Moving an iron sphere along a path with an electromagnet

  1. Oct 10, 2015 #1

    So I am working on a project that requires the movement of iron nanoparticles (let's assume 25nm in diameter, and let's assume the sphere is uniform and pure iron) through a (non-magnetic) gel using an externally applied magnetic field. Let's assume the total distance I want to move the particle is 5cm. The force I need to exert on each nanoparticle individually to move them through the gel is at most 20pN. I have no physics background, but what I think I know is that to move a magnetic particle along a straight path with constant force I will need to apply a magnetic field gradient that is roughly equivalent at each point along the path. I believe this magnetic field gradient should be on the order of 50T/m.

    Is it possible to achieve this using an electromagnet? Is there a name for this type of device that I can look up? How might I go about creating such a device if it is possible? I'm just looking for someone to point me in the right direction. Please assume if you post a formula that I'm a 10-year old with only a basic understanding of electromagnetism.
  2. jcsd
  3. Oct 11, 2015 #2


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    2017 Award

    Staff: Mentor

    50 T/m is possible, but getting this over 5 cm is not trivial. As an example, state-of-the-art LHC magnets have ~250 T/m over a few centimeters.
    There are a few applications (e.g. MRI), so it might be possible to buy those magnets. Creating one yourself... I don't know. The LHC magnets are superconducting, with normal-conducting magnets it will be challenging to get high gradients and you certainly don't have the tools to make very good coils.
  4. Oct 11, 2015 #3


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    Staff: Mentor

    You sell yourself short!


    Can you say more about the application? At what depth in the "gel" will you need to move the nanoparticles? Are there any contraindications for high magnetic fields in this application?
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