Update on new magnet design
Ok, so I definitely owe you guys an update. I've been working with a number of people to develop a new magnet implant that's significantly better than what people are implanting now. It's more than simply a better coating. We've been working to determine the optimal shape, and comparing axial and diametric magnetization effects. I've also hinted at the application of other layer to focus the magnetic field. There are still a number of hurdles that this project has yet to hop, so I'll focus on what's probably the most important aspect: coatings.
I still have my first magnet implant. It's a V&P, parylene coated. It's held up surprisingly well. It's not an N52 however and doesn't compare. I figured that there had to be better. I ordered N52s from SMM. The parylene is simple too thin and fragile. This lead to my first attempt at a new coating: Dental resin. As I've said before no one has actually ever reported a rejection to me. Another grinder who coated his own reported problems however which got me doing more research. Dental resin isn't optimal because A) there is no research indicating or approving it for implantation, much less long term implantation, and B) it's a porous material which is begging to be colonized. So I began looking at other plastic/resin/epoxy solutions.
I tried... Atom Adhesives, Masterbond, Epotek. I tried different versions from different companies, and yet each type really left something to be desired. It was also all very difficult to work with. I built molds and baked and cured and ground. Not a single one really impressed me.
Ok, so this is where I broke from my initial "Grinder Economics" vision. What I've really always wanted to maintain is essentially an educational type of atmosphere. Sure, I want to sell you stuff. I want your money so I can do cool things... but I don't want to rip you off. - (Begin Rant) I seriously take issue with advertising. The point of it is to make money, not explain why a service or product is better. I totally want what I do to be something you can replicate yourself. The point of selling resin coated magnets wasn't because you can't do it yourself. No, I explained exactly how to do it. But, since I already have everything including experience making them I can save you the difficulty and perhaps even money. I wish I could stay with this model, but unfortunately we really do need a better method than glue sticks on refrigerator magnets.
So on to other methods involving other people:
The most obvious... more Parylene. Why not do multiple depositions? Well, the vapor depostion of parylene can only apply so much per run and because it's essentially a surface meant to prevent crud from adhering, multiple deposition runs don't really add to the mechanical strength to the degree I expected.
I could list about 4 other things I attempted, but I'll cut to the chase as to where I'm at:
Metals. There are a couple of metal options that are very, very promising. I'm rather found of Titanium Nitride. Titanium Nitride is commonly used in orthopedic implants and screws. It's a gold color... the same golden tips you see on drill bits. The problem with TiN is the temperature. It's applied via physical vapor deposition - sputtering. Basically they shoot it through a plasma arc and it sticks to the magnets. The temperature is around 500C. I had samples made and tested - perfect. No cytotoxicity. The coating was thin around one edge, but this was expected and wouldn't occur in the final product. The big big problem though? Sintering temperature and unrecoverable losses. I swear I've gotten so many different numbers regarding the curie temperature of neodymium. No matter what, if you get these magnets hot they lose strength But they can be remagnetized. Too hot though, and there are physical changes that occur in the neodymium that result in an unrecoverable loss - can't remagnetize it. Now, I kid you not... one source gave me the unrecoverable temperatures as starting near 950 - 1000C. Another reported to me that this is incorrect and that the curie of N52 was closer to 350C. The literature seems to hover right around this number. So, having a TiN applied may result in a partial loss of magnetism. I was told that this wouldn't be much. The example given was the if a magnet was originally 1000 gauss, after remagnetization it may be only 950 gauss. To put that in perspective, its a difference that we as humans aren't able to detect. I'm still not entirely happy with this though. I've been working with another person who uses a CVD method which can be performed at cooler temperatures. This is a work in progress.
Another option, and one that I had long ago ruled out but have recently reconsidered is PTFE. (Teflon). PTFE has that same temperature issue... under normal circumstances. It's also thick and bulky. I've found a few biomedical coating specialist that use a PVD system with PTFE and they can do it under acceptable temperature ranges and in an acceptably thin layer. I'm actually considering this route heavily right now. It doesn't have the beauty of titanium. I mean titanium is pretty and simple, BUT PTFE can be applied conformationally and account for some of the modified shapes and other options I'm experimenting with. It's pretty cool stuff.
I have a few other methods I'm considering - for example cold spray deposition is this really cool new tech that shoots particles at supersonic speeds at room temperature to form a coating. 316 surgical steel can be applied this way... but I haven't been able to find someone actually using the process. My biggest restriction so far has been of course funding. I've been working with Amal from Dangerous Things as of course the guys from SFM, but these processes are rather costly when your not entirely sure that the end product will work. I'm going to keep working on this and an tentatively planning on having a new magnet product out by August. Hopefully sooner.
I still have my first magnet implant. It's a V&P, parylene coated. It's held up surprisingly well. It's not an N52 however and doesn't compare. I figured that there had to be better. I ordered N52s from SMM. The parylene is simple too thin and fragile. This lead to my first attempt at a new coating: Dental resin. As I've said before no one has actually ever reported a rejection to me. Another grinder who coated his own reported problems however which got me doing more research. Dental resin isn't optimal because A) there is no research indicating or approving it for implantation, much less long term implantation, and B) it's a porous material which is begging to be colonized. So I began looking at other plastic/resin/epoxy solutions.
I tried... Atom Adhesives, Masterbond, Epotek. I tried different versions from different companies, and yet each type really left something to be desired. It was also all very difficult to work with. I built molds and baked and cured and ground. Not a single one really impressed me.
Ok, so this is where I broke from my initial "Grinder Economics" vision. What I've really always wanted to maintain is essentially an educational type of atmosphere. Sure, I want to sell you stuff. I want your money so I can do cool things... but I don't want to rip you off. - (Begin Rant) I seriously take issue with advertising. The point of it is to make money, not explain why a service or product is better. I totally want what I do to be something you can replicate yourself. The point of selling resin coated magnets wasn't because you can't do it yourself. No, I explained exactly how to do it. But, since I already have everything including experience making them I can save you the difficulty and perhaps even money. I wish I could stay with this model, but unfortunately we really do need a better method than glue sticks on refrigerator magnets.
So on to other methods involving other people:
The most obvious... more Parylene. Why not do multiple depositions? Well, the vapor depostion of parylene can only apply so much per run and because it's essentially a surface meant to prevent crud from adhering, multiple deposition runs don't really add to the mechanical strength to the degree I expected.
I could list about 4 other things I attempted, but I'll cut to the chase as to where I'm at:
Metals. There are a couple of metal options that are very, very promising. I'm rather found of Titanium Nitride. Titanium Nitride is commonly used in orthopedic implants and screws. It's a gold color... the same golden tips you see on drill bits. The problem with TiN is the temperature. It's applied via physical vapor deposition - sputtering. Basically they shoot it through a plasma arc and it sticks to the magnets. The temperature is around 500C. I had samples made and tested - perfect. No cytotoxicity. The coating was thin around one edge, but this was expected and wouldn't occur in the final product. The big big problem though? Sintering temperature and unrecoverable losses. I swear I've gotten so many different numbers regarding the curie temperature of neodymium. No matter what, if you get these magnets hot they lose strength But they can be remagnetized. Too hot though, and there are physical changes that occur in the neodymium that result in an unrecoverable loss - can't remagnetize it. Now, I kid you not... one source gave me the unrecoverable temperatures as starting near 950 - 1000C. Another reported to me that this is incorrect and that the curie of N52 was closer to 350C. The literature seems to hover right around this number. So, having a TiN applied may result in a partial loss of magnetism. I was told that this wouldn't be much. The example given was the if a magnet was originally 1000 gauss, after remagnetization it may be only 950 gauss. To put that in perspective, its a difference that we as humans aren't able to detect. I'm still not entirely happy with this though. I've been working with another person who uses a CVD method which can be performed at cooler temperatures. This is a work in progress.
Another option, and one that I had long ago ruled out but have recently reconsidered is PTFE. (Teflon). PTFE has that same temperature issue... under normal circumstances. It's also thick and bulky. I've found a few biomedical coating specialist that use a PVD system with PTFE and they can do it under acceptable temperature ranges and in an acceptably thin layer. I'm actually considering this route heavily right now. It doesn't have the beauty of titanium. I mean titanium is pretty and simple, BUT PTFE can be applied conformationally and account for some of the modified shapes and other options I'm experimenting with. It's pretty cool stuff.
I have a few other methods I'm considering - for example cold spray deposition is this really cool new tech that shoots particles at supersonic speeds at room temperature to form a coating. 316 surgical steel can be applied this way... but I haven't been able to find someone actually using the process. My biggest restriction so far has been of course funding. I've been working with Amal from Dangerous Things as of course the guys from SFM, but these processes are rather costly when your not entirely sure that the end product will work. I'm going to keep working on this and an tentatively planning on having a new magnet product out by August. Hopefully sooner.
Tagged:
Comments
In terms of FEP.. yeah your totally right. I was really grouping all the fluoroplastic. I've looked into FEP, PTFE PFA ETFE etc. They're pretty similar, and a number of versions of each would suit our purpose. The thing that I'm going for here though is a coating thats been extensively tested for long-term implantation safety etc. And one that I can find a manufacturer for. The material data on FEP looks great, but I haven't found anybody who specifically uses them for implants. Since you point it out, I'll look into FEP further though.
Im sure those are the best,but if im wrong, can someone point me in the right direction?
https://steve-haworth-modified-llc.myshopify.com/collections/magnets/products/copy-of-1-1-2-38mm-x-1-4-6mm-hollow-center-heart-1
Also, cold deposition... man, I really explored this. There is so much potential but no one seems to really be doing it outside of colleges. I couldn't find anyone. What I ended up going with is "proprietary" at the moment. I'm not trying to be a deusche, but because I'm working with other folks it wouldn't be good to get scooped. If it doesn't pass testing, or once I have some finished product I'll let y'all know the coating. So far, it looks like the ultimate solution.
The shape issue - this is where a lot of improvement can be made. Your right that a torpedo shape would work well, particularly because it would deform tissue and press on the surrounding mechanoreceptors more than a disc through axis would. In fact, the shape I'm eventually going to push for is more of an oblong concave surface. I have some technical drawing I worked with an engineer to make that shows the optimal field line shaping stuff... but having shapes like I'm describing provides a surface with "nooks and crannies" which facilitate adhesion and fouling. It's all a work in progress. I'm totally down to discuss these things.