Found a possible way to levitate magnets for coating them in a solution
  • Check out this video on induction levitation for neodymium magnets. Its possible we could do something similar to allow for perfect coatings for magnets in a solution. What do you all think? The aluminum is used as it allows for an inductive field which makes levitating the magnets much easier and a simple jig could be created to keep the larger magnet at a perfect distance for lifting the smaller magnet.
  • I also found this levitation video as well showing another possible levitation method. This youtube channel is a goldmine for this type of thing!
  • Diamagnetic levitation gives you very little space to get your coating gas inbetween. Properly controlled magnetic levitation works pretty good, you don't even need the massive aluminum plates/tubes. A thinner copper/aluminum bands will work just fine to reduce high frequency oscillation movement. All that's left to add is a simple control circuit. PD will work fine, if you use that much aluminum you can probably make it work with a very simple 2-state control too. Have a look at all the hall-effect switch magnetic levitating devices on youtube. They work great for bigger objects, but if you dampen small magnets with aluminum/copper they should work fine for small ones,too.
     
    Picture of my current protoype (without control circuit).
     Battery for size comparison. The thing features a plastic frame, a small coil, the copper cage to keep things stable and an (analog) hall sensor on top of it. There are many similar ways to do it but they pretty much all boil down to having a sensor which registers the position and speed of the magnet and some control loop to keep the magnet at the desired values. The more metal-cage you add, the slower your magnet will move and the easier it is to find stable parameters.
  • Do you have any ideas for a sensor to watch the small magnet? I was thinking something like a compass chip like these from adafruit would work well for that 
    if you pair them with a super fast micro-controller like this guy
    you should have no problem stabilizing it. that WICED is also pretty cool as it has a separate integrated web server radio so you could even controll the whole thing from a phone of computer over wifi. 

    EDIT: that hall effect thing is pretty sweet as well! 
  • for the size of an implantable magnet (like just a few mm) you need a rather fast sensor. Last time I tried my magnet got unstable when adjusting the power of the coil slower than 400Hz. Most magnetometers are made for something like 50 to 150 Hz so those are a bit slow. Hall effect sensors have the disadvantage of being single-axis only (unless you get special ones) but they are very fast.

    You may just get away with a magnetometer if you use enough aluminum/copper and provide a small enough hole in it. But you probably are better off using a fast sensor to give you a bit of extra space. You don't need super fast microcontrollers. A regular arduino will do fine. You don't even need that tho. The control loop can easily be build using op-amps. You may want to use two hall effect sensors. one on the bottom and one on the top end of the coil. That allows you to subtract the coil's magnetic field easily so you can determine the position of the magnet with less difficulty. This only works with analog hall effects sensors (not hall effect switches).