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Methods of acquiring gold and TiN coated N52 + implantation idea + new method of testing coated N52
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Displaying comments 91 - 120 of 123
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Thermal, I don't think Ben's trying to discourage you. He was involved in a previous buy of magnets which were treated aggressively and which eventually failed. His point is valid in that certain tests which seemed much harsher then the body didn't cause then to fail.. but those replicating body conditions did. I feel that this is a productive discussion. My question was, what are you doing differently then all the things done previously? Ok, using something like gold as the undercoating may work. I'm interested. Parylene works if applied correctly. If you go that route, try to get a guarantee from the company that coats them. The big issue with parylene is quality control. One of the forest magnets I Implanted was from v&p. They make magnetic stir rods. The coating is great.. but parylene coated magnets from super magnet man always fail. I've gotten a few batches over the years. One batch.. the coating was poorly bonded and peeled off. Another batch when I tested ended up being coated with some kind of resin which wasnt biocompatible. If you do go the parylene route you might as well skip the TiN. Parylene is good enough that it would make the TiN irrellevant. So let's brainstorm this out? What are your current ideas? Gold and TiN?
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You know what you might consider? Teflon. It's fantastic. The reason I've never gone this route is because I couldn't find anybody who did it thin enough.. but it's biocompatible and not terribly expensive. It would still be better then silicone.
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Another option to spray-coat it with biocompatible resins. There are companies which offer ultrasonic based spray coating for very thin and even coats. Might be worth to give those companies a call. The process is usually done at room temperature and requires very little special care (except it needs to be optimized for the viscosity of the liquid which gets sprayed on). Virtually no mechanical or thermal stress on the magnet. plus you'd get a very smooth finish due to the liquid nature of the coat in first place. Maybe starting with that UV-curing resin from loctite would be an option.
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At the moment I am heavily considering Cu/Au+PTFE+TiN.I would prefer Au over Cu however Au doesn't bind well. The PTFE binds very well and is also a dielectric layer inbetween the two noble metals. PTFE is also biocompatible, however I will only be able to chemically test that the top TiN layer is fully intact.I'm talking to a manufacturer about the size of the PTFE coating. Cassox what would you recommend the micron thickness of each layer should be? I am also taking account the cathode/anode ratio to reduce galvanic corrosion.Having the right cathode/anode ratio and having a dielectric material inbetween the two noble metals should entirely fix galvanic corrosion.@ThomasEgi that looks interesting, i'll definitely look into it. Would you mind pming me the names of a few resins and companies?
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I'll get back to you about thickness. I seem to remember 15 microns was about what most places do. Did they say they can coat TiN over Teflon? Crazy.
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+1 if it's possible to do PTFE-TiN. This sounds like it's meeting a lot of necessary requirements. :o But if we are looking around 30-40 microns already between those two, would definitely suggest attempting to minimise any other layers as much as possible. Here's where Au's thinness would come in super handy to create that di-electric union around the PTFE. ^^ Does there have to be a base coat of Cu, if Au isn't an option? My thoughts are if not Au, probably delete the under layer and take advantage of PTFE's adhesion to again, minimise coating thickness and remove redundancies. Is anyone familiar if PTFE/TiN are going to have cavitation issues? Just trying to shoot things in the foot. ;3;
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Would Teflon over gold be good enough without the TiN? I think Teflon is a soft, slippery plastic and often used on magnetic stir bars. It should handle about any chemical test unless there is a defect. I think any strength of bleach should be fine with Teflon so that might make sterilizing it easy. Just need to get the thickness right.
If the Teflon coating was done good enough, might not even need the gold.
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Birdhandz could you provide a source for the pH that Teflon begins degradation? I was assuming Teflon would easily degrade, that's why the TiN layer is necessary. The Au/Cu layer is necessary for testing but I am concerned about adhesion issues between Au and Teflon.If Teflon can withstand bleach then it makes TiN useless especially considering the coating test wouldn't work.The Cu will help with adhesion and will increase the tensile strength of the magnet. I am also looking into potentially using Ni because it can be tested for and has a higher tensile strength than copper. I'm looking into the adhesion properties of nickel before I decide which material to use.We were just pledged another $20 and I am waiting for a response from an investor.
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@birdhandz one of the most successful constructions of magnets is Parylene with an Au undercoat, past experiences observed. ^^ What makes PTFE tricky is thickness. Dental resin has the same issue... it works great, but it's so thick that Its hardly practical. ;_;
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I don't think pH matters with the Teflon. I have looked at several charts of the chemical resistance of PTFE and didn't find anything common that degrades it.
http://www.componentsupplycompany.com/PTFE-Chemical-Resistance-Data.html
That chart shows it as being resistant to fuming sulphuric or nitric acid or caustic soda. Also resistant to acetone, and other solvents.
Biggest problem sounds like getting the coating thickness right.
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I did some research and agree with you that bleach will not effect Teflon. I'm looking into getting the magnets coated in Ni/Cu/Au+PTFE. I'm waiting for a response as to how thick the Teflon coating is going to be.It would be helpful if everybody pm'd me all the companies they know that can coat/manufacture magnets. I am trying to get a hold of Puzbiks to get a status on his investment.
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@ThermalWinter unfortunately I have no recommendations. I only researched the topic from a theoretical end and discovered there are industrial applications for spray-coating. You can probably find a number of companies by searching for ultrasonic spray coating on google/youtube
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I just noticed this picture from a link in a different thread here that is the silicon coated Steve Haworth ones.
The first thing that caught my eye was the visible parting line. It might be a reflection or something I'm seeing but it looks like the centers are rough. Hopefully it is just a reflection of the magnet showing through clear silicon.
The other thing I noticed was the thickness of the coating. I never tried coating a magnet with any type of epoxy or silicon before but I would hope to get a thinner shell than that.
Can the epoxy or resin be thinned with heat or solvents enough to allow it to be brush painted on? A magnifying glass, a good light, and a tiny artist's paint brush should make coating it fully without adding an excessive amount of extra size and weight possible. If it sticks to itself, two thin coats might be better than one thick coat.
Would curing it in a pressure chamber help or hurt the finish? A vacuum chamber would probably be better but a pressure chamber sized for these tiny magnets could probably be PVC water pipes/fittings and a cheap tire pump. This same idea might be useful in the testing stages. If the magnet was submerged in salt water and then the container was pressurized with compressed air, would that help force the liquid into any cracks or pinholes?
I'm sure coating them yourself is a lot more difficult than it sounds like it should be. The latest idea of Ni/Cu/Au+PTFE sounds as good as any if it can be done.
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You know, I've actually been considering toying with the idea of a coat that can be brushed on the last couple days. #_# spoopy. I'd stay away from thinning solvents myself without higher end equipment... If it goes in the resin, it's going to need to come out. Our bodies hate acetone. Or worse. ;_;
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Coating is very difficult, expensive, and messy. The necessary equipment and material is expensive and it will be very difficult to get evenly distributed coats across the entire magnet.On top of that many of the materials require very high temperatures to be used in the process and that means the magnets have to be remagnetized (Or in my manufacturers case magnetized the first time) after they have been coated. If you wanted to go down this route you can but it is not as easy as it may sound, that's why there are companies with this service.
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If the companies can and will coat the magnets, that's the best way to go. They know how to do it and have the tools to do it right.
The DIY coating methods might not be as difficult or expensive as you might think though.
https://www.youtube.com/watch?v=RKkIgH2wqSw
I need to watch the video again to be sure but I think this is the type epoxy used.
https://www.atomadhesives.com/FDA-Grade-Food-Medical-Epoxy-Adhesives/FDA2T-Food-Safe-Medical-Grade-FDA-Adhesive
Again, I need to watch the video to confirm my memory and to try to see the size pack used in the video. The smallest 2.5 gram pouch is only $4.99 but I haven't checked what shipping adds to that cost. Cheapest shipping for me was $4.67 so around 10 bucks for the epoxy. I don't know how many magnets the 2.5 gram pouch can coat but probably at least a few of them. Maybe more.
I still think having some real company make them is the way to go for getting them if the cost isn't too high. If you only wanted a few magnets and were willing to do the work and testing, trying to coat them yourself might be an option.
I'm tempted to order a pack of the epoxy and try coating some of my cheap ebay magnets. The video showed heating them to cure the epoxy but 24 hours should do it at room temperature. It could take some practice to get the coating process figured out but it could be useful for other projects besides the magnets.
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On a side note, I've never had success using a vacuum chamber. I thought I'd be able to pull out solvents or air bubbles.. but it doesn't work out.
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I've been toying with an idea now for a few weeks. Do you think we could, either through 3D printing, machining, or injection molding, make a small, sub-millimeter thick canister out of HDPE or another biocompatible plastic that's open on one end, slide our magnet into that, and then just ultrasonically weld the end shut with another disk?
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vacuum-forming HDPE foil/sheet would be easiest. ultrasonic welding would be one way to do it. Medical grade glue would be another.
while you'r at it, try to aquire some FEP foil too. -
Birdhandz there are two types of epoxy that have different cureing methods. The first cures immediately when mixed and has a small time frame to coat the magnets and the second needs to be heat treated to cure. The heat treatment would be very difficult.I am seriously considering epoxy though. I am looking into doing it on my own or potentially involving a company that can do a medical grade epoxy.My goal is to make magnets coated in Ni+Epoxy+TiN. Galvanic corrosion between the TiN and Ni is negated by the dielectric effects of the Epoxy. The Epoxy (Preferably coated and tested) will also act as a second bio compatible layer.I believe we can use the same alkaline/acidic solution test on the epoxy to determine the integrity of the outer coating because epoxy is known for its chemical resistance. unfortunately though I can't find the pH of when epoxy begins to degrade.The Ni layer is useful because of it's high tensile strength and good adhesion properties. It can also be used to test the integrity of the epoxy and TiN aslong as the epoxy is tested before the TiN is added.If anybody has a resource on where we can get quality epoxy coats I would appreciate it. If you are seriously considering attempting to coat your own magnets with epoxy PM me and we can work on it.
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The epoxy I am now considering is the Atom Adhesives FDA15.
It is low viscosity so might be better for "painting" on a thin layer.
It's an electrical insulator if that makes any difference. I'm not sure if the TiN can be coated on top of it. It says it is resistant to mild acids and alkalies but didn't state the pH of them. Didn't mention bleach either so I don't know if it is resistant to that.
It can be cured @ 65 degrees C. (149 F.) in 1 to 4 hours or in 24 hours @ 25 degrees C. (77 F.)
It has an operating temperature of -70 to 140 degrees C. so should handle autoclave sterilizing. Wouldn't be good for the magnets but for other implants it might be a good sterilizing method.
I assume the epoxy has a limited pot life once it is mixed together even if stuck in the freezer so it probably needs to be used all at once or within a day or so. @Benbeezy might know how long freezing it keeps it good if he is still following this thread.
I want to try coating some of the best ebay parylene coated magnets I have. I would probably practice coating a cheaper nickel coated magnet before using the parylene coated ones. The levitating device that @ThomasEgi built would have a better chance of getting a smooth finish but I'll probably just use parchment paper to keep the epoxy from sticking to anything.
It will be a while before I order any of the epoxy but I'll let everyone know how I make out with it if I do get some.
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My only concern in regards to painting the epoxy onto the magnet is it will be very difficult to get a complete coating. The strands of the brush may create microscopic impurities in the coating. I am looking into a possible method of coating magnets in medical grade epoxy and will post it here when I have more information.I am very close to finishing these magnets. If I can get the epoxy layer as a dielectric layer it will solve galvanic corrosion and is also an effective second biocompatible layer. I can get the magnets coated in TiN once they have been coated in Ni+Epoxy.As close as I am to developing these magnets we are fairly far from our financial goal. I lost contact with Puzbiks, our main investor. We currently need allot more investments and purchases in order to develop but when we do we will have a consistent supply of biocompatible magnets.
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using vibrations or relying on any surface tension of the epoxy might solve the microscopic impurity problem on its own. maybe treating the the surface prior to the epoxy can help with the epoxy sticking to it better.
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Except for your (@ThermalWinter) comments on this thread, I can't find any other mention of Puzbiks. Are you sure you are spelling it right?
P.S. I'm not sure I'm doing the tagging people right. I haven't gotten any email notifications from this site even when someone tags me. Don't know if that feature stopped working or not. Doesn't matter much on this thread since I read most of the new posts anyway but I have a feeling I might be doing it wrong.
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I stopped tagging users since it doesn't seem to be working. Puzbiks is the username he messaged me on. He still hasn't responded to me and I am working out getting epoxy at the moment.I'll post when I have more information, for now we need more money to fund development
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I have confirmed that epoxy is possible. I am currently researching specific epoxies that have the properties I need and am contacting manufacturers to get the magnet coated in Ni+Epoxy+TiN.
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I found a manufacturer willing to coat the epoxy and I can also request that they perform tests on the coating to verify it's integrity, unfortunately this will cost more. The magnets will only be magnetized after they have been coated so that I can guarantee the strength of the magnet.I am currently working out the tests I want performed by the manufacturer and am looking into getting the epoxy layer examined with a microscope after soaking in a mildly alkaline solution before they are coated in TiN. The manufacturer will also test the TiN layer using the diluted bleach solution and a chemical test for nickel before sending them to me. I will personally test the TiN coating a second time to guarantee safety.Unfortunately since we don't currently have funding it doesn't seem like I can get these magnets manufactured. I am looking into the exact cost but I can safely estimate $400 needs to be invested to get these manufactured. Each investor will receive magnets according to how much they invested however I still need to calculate the exact cost per magnet.I'm considering starting a new thread since this one has almost entirely changed from it's original purpose.
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Having the manufacturer do the testing sounds like a very expensive option but this is your project so I won't try to tell you how to do it.
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Somewhat off topic but I just ordered a small pack of the Atom Adhesives FDA15 that I mentioned before. I ordered the 2.5 gram pouch which I have no idea how many magnets that could coat. The 25 minute pot life has me concerned so I am thinking about mixing it myself instead of mixing it all at once. I intend to coat them similar to what Benbeezy's video shows using parchment paper to keep them from sticking. I'll leave them cure at room temperature instead of using heat which is why I don't want to mix it all at once because it will likely take at least two times to get a full coat.
I'll start my own thread when I try this idea if it looks like it might actually work.
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Not parchment. Wax paper.
Displaying comments 91 - 120 of 123