Controlling and/or manipulating the magnetic fields

edited February 2015 in Magnets
I plan to have the magnets place in my fingers by the end of this semester. im not particularly well versed in how this works so I may ask one of the scientific minds at my college to help me. As I was thinking about the procedure I wanted to take it to the next level, so my question is, would it be possible to manipulate these magnetic fields if say there was some sort of power source and/or an electrical current running through the hand/body, this is all theoretical, and again I am not well versed in this subject, so forgive me if this question is moronic, i was just wondering if someone has at least thought about it.


  • You need a coil to induce a magnetic field using an electrical current, you cannot do this by simply running a current through a magnet (even if you tried, it'd just conduct through the plating).

    What would the goal be of manipulating the magnetic fields?  Do you mean you want to be able to turn the magnet on and off?
  • This project would entail a lot of things previously discussed in this forum. An electromagnet is simple to make: insulated wire wrapped around a core. Here are the problems which would have to be addressed:

    Size: The overall size of the device, and the number of turns of wire around the core provide the upper limit of the device. The bigger it is, the more power it will require, the more heat it will produce, and the more difficult insertion will be.

    Heat: The size of the wire gauge and the type of wire will determine resistance and the amount of heat produced. You don't want to have something getting to hot under the skin.

    Power: A battery may work, but for how long? If you're going to recharge the device, then how? Many suggest and induction coil charger, but this increases the size of the device and depending on your design may require many hours for a charge. Beyond this, rechargeable batteries eventually fail and contain nasty poisonous crap that can either kill you or cause necrosis of the tissue if you bio-proofing fails.

    Control: Are you going to have an on off switch? Because you say "manipulate" I assume you want to be able to ramp the power up or down. The circuit to do this increases the size and complexity of the device, and I'm not sure how you'd incorporate a mechanical switch that's bioproofed. Perhaps some kind of RF transmitter reciever? But this take even more power, complexity, and size.

    Bioproofing: Not the biggest issue. I'm sure you could coat the hell out of your device, but this once again increases the size and if you incorporate any nasty metals or batteries a failure would be catastrophic.

    Overall, I think this would be a great project to collaborate on. Because each of these issues would NEED to be addressed for ANY major project, this relatively simple circuit might be a great starting point that would provide data/technique/experience for later larger projects.

  • few additions:

    Heat is not so much a problem, the body can transport a lot of it away, ways more than you would want to feed any implanted device with.

    Power, electromagnets demand tons of current. i'd drain any mattery in a matter of minutes. Inductive sollutions would be pointless as you'd have to carry around a big inductive supply,too. so you could connect the electromagnet to a battery with all benefits but no additional hassle.

    overall. having a tiny electromagnet in your fingertip would be pretty much pointless. big problems to overcome and i coludn't come up with a single possible use.
    even for a starting project it's not really suited. altho other circuits may be a bit more complex, they are easier to handle (due to less current demand) and a lot more useful.
  • Hmmm... I'm going to have to look into how pacemakers are powered. Those bastards last 8-15 years.
  • they have a very very very low energy use. a magnet would eat several billion times more energy.
  • Valid point. Looking into pacemaker power systems though led me to great info. Did you know that they used to make plutonium powered pacemakers? Wow. 80-100 years life. Not that I would use one even if I had a pile of plutonium lying around. Ok, so this is how manufacturers of pacemakers have addressed the issues above:

    Size: Pacemakers are relatively bulky but this is mediated by long electrode wire. The pacemaker device itself is subcutaneous in the upper chest with an electrode passing into the appropriate region of the heart. Is this useful to us? Well, it could be... if one of two innovations occurred. If one were to place the "power pack" or bulk of a device in the abdomen or chest, one would need either biosafe wires (There is a thread for this) or conductive tattoos (There is a thread for this) or some combination of both.

    Heat: Not an issue for modern pacemakers. I couldn't find specifics on the voltage output, although I know that they must be >4 millivolts. Pacer spikes show up on ECGs with a 4 millivolt or so spike and some of the voltage must be lost before being sensed. Heat WOULD be an issue with any device of larger draw.

    Power: I really liked this read - ( Very interesting. Lithium Iodine are apparently top of the line at this point. Unlike earlier sources, Li batteries lose very little charge over time at rest and can last over 10 years (for a pacer). I can attest to seeing patients (Not MD, RN) that have had them for longer without issue. I've also seen patients who have failing pacers at like year 6. Another advantage is that Lithium Iodine doesn't produce gas and thus can be sealed inside a biosafe container. Too much draw though and these suckers can get hot or even explode. Something to keep in mind. Early models DID attempt to use induction charging, but these were forgotten as it requires the patient to maintain the charge. Many think this is too chancy.

    Control: Yes, modern pacers have some serious functionality. Pacer reps go into hospitals and query pacers all the time using an RF interface. From what I've read, half of the power used by modern pacers are the microcontrollers. Pacers no longer blindly discharge; they have many many different modes such as "On-demand" pacing which fires only when the heart "waits too long." So, it seems the optimal means of control may end up being a non-mechanical option... which unfortunately means a very small but constant drain on power. PERHAPS the best way to do this would be a Lithium Iodine battery to power the microcontroller over a ten year period, and an induction charged battery pack for the actual function which may require much larger voltage, but for short periods.

    Bioproofing: My god, this I think was the best part: Hermetically sealed titanium units. I've been reading a lot about welding titanium, which seems to be a bit complicated.... but if we had one person skilled at welding titanium, then bioproofing would be a moot issue for many types of implants. Titanium also prevents interference from devices such as microwaves. I picture a small sealed titanium unit coated first in parylene, and then in a more durable biosafe material. This seems optimal, and would have the benefit of sequestring the really nasty stuff inside the battery from release into the body.

  • So! Instead of an electromagnet... I think a timing unit would be a great starting point. Something akin to an alarm that goes off each hour, or perhaps even a countdown. This would be VERY similar to a pacemaker and we could use a lot of the same solutions. It could be externally programmable, powered by Lithium Iodine, sealed in titanium...   My question though is which sense would be stimulated? Could we make little vibration units that are magnetic and not mechanical. A vibrator from a pager is too big and too electrically expensive.
  • Think of one of the rice grain sized neomydium magnets. If one made a coil around it like an electric motor, and had a weight offset to make it vibrate... then placed the whole thing in small titanium housing about the size of a pill. Or how about a solenoid which thrusts the core forward to strike the titanium housing, like ringing a bell. Actually this might be optimal because the entire unit would be one.

  • about batteries: i'd prefer a battery that's save with a high cycle lifetime over one that's expensive,hardly available ,prone to failure and not rechargeable. we have another threat about power sources, so far. regular li-fe-po batteries combined with inductive charging is the most realistic approach.

    titanium cases, i'd have no idea where to get it from. guess welding it would require tooling etc too. for now the best options we have is ptfe and parylene-c. both are readily available.

    as for feedback. you'd most likely want to go with regular electrodes. any sort of magnet or mechanical motion eats quite a lot of power. so for most basic feedback you'd probably end up tingling a bunch of nerves in your skin. tapping directly into neurons would be possible if you can get hands on the right electrodes and someone who can implant it. simply putting 2 electrodes into the skin would be a tingling sensation at first. and over time, your brain will probably adapt to whatever makes sense.
  • I can think of a use for an electromagnet, but I'd only need it to work for 30 seconds or less at a time. Maybe capacitors would work for that? 

    It might be handy to have an electromagnet and use it to switch other implants on and off via reid switch. Bar tricks would be awesome too. 

    As far as hermetically sealed titanium goes, there are 3d printing services that can do that.

  • No, the charge density for capacitors is much lower than for batteries, and as such they are even less feasible for powering electromagnets, or anything that's supposed to be implant-size really.

    I would still suggest avoiding electromagnets in your designs.
  • Just a comment about pacemakers... they have a plutonium battery, that's why they last 8-10 years :) I half-expected to see a flux capacitor in there somewhere, but no, just a plutonium power cell... and it puts out far less than 1.21 "jiggawatts"

    there are some very interesting developments with carbon nano capacitors happening right now... for the moment they're called (lamely) "super super capacitors". nothing commercially available, but very interesting. 
  • DirectorX wow, being able to order custom titanium prints is great.
  • No, there were a few models of pacemakers made throught he 70's made with plutonium. They were very large and incredibly dangerous as mere microns of plutonium is a death sentence. The "battery" life of a plutonium implant is around 80 years. Modern pacers use Lithium Iodine batteries, which are much safer and still provide a good 10 years or so of service.
  • Ah interesting. I still like to think there are people walking around with nuclear powered pacemakers.
  • Oh yeah. They're still out there man, although becoming rarer. I was reading something about difficulties traveling to some countries. Also, they have to be cut out after death.
  • off topic from the thread title, but related to what people were talking about with the pacemakers.
    for those that didn't see this:
    and referenced paper:

    I doubt any of us are up to making neural interfaces like that, there is some potentially useful info about making bio-safe containers.
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