Any and all information on this page (and site, in general) is for informational purposes only, and should only be used as such. Nobody on this site will endorse or support a person to put any information here to application, and all given information is only provided for, again, educational purposes. The following is listed to help establish things that have little evidence and support, to those that have none or proven to be harmful/dangerous/unideal. This should be thoroughly understood before proceeding. Proceed with appropriate discretion.
There are ultimately different flavors of magnets. A few of the variables explored here relate to:
- Shapes - Sizes - Compositions - Coatings
All of these can effect characteristics.
The most common shape utilised in implantation is the cylinder, due to it's profile shape exposing minimal corners, and an even surface in each direction that has no 'weak' sections to be broken off, while still retaining a capacity for a 'flat' surface to lay neatly underneath the dermis.
A much flatter cylinder, resembling a coin, exhibits an area with no sharp corners to inflict trauma into tissue or be weak stress points to break off and compromise the coating/internals. This is by far the most common profile, and is used in most magnets for implanting and sensing fields due to their high sensitivity and responsiveness, with little mass to move. These are also relatively easy to manufacture, compared to intricate or organic shapes. Sometimes, longer cylinders, such as rods, are used. These can provide a larger mass of magnetic material, for stronger fields to preform 'tricks' such as lifting ferrous objects, but do not provide as much sensation because of their larger bulk to move. Spheres have a very easy tendency to 'flip' in the tissue, causing movement which can cause discomfort, and possibly creating scar tissue from the body attempting to heal around an object that can move with a smooth surface. Cubes or Rectangular Prisms expose corners, which under pressure or impact may cause tissue damage, as well as expose weaker sections that may be more easily damaged. If a cube were to 'flip' in vivo, it could cause severe discomfort. The use of Ellipsoids may provide very effective replacements to rods, but may prove difficult to manufacture or coating. Utilization of magnets with perforated holes may exhibit further stability in the body and promote blood flow and tissue health. The Difficulty with this is a proper coating over the surface, and making sure the holes are not creating areas to become septic. This is very complicated.
Volume of the magnet is also important to take into consideration. Factor to consider:
In proportion to the magnetic material used, sufficient quantity of material needs to be used to interact with magnetic fields, lift ferrous objects, or do whatever else the implant is desired to do. The size of the magnet in vivo needs to be kept to a manageable size, as to not actively interfere with blood flow to the skin. The Volume-to-Strength ratio. The larger the mass of a magnetic object, the less effective it's going to be due to the extra weight that is needing to be moved. Smaller magnets have much less weight to move around, but are also much more sensitive to extra inert material added into its total weight. Math is important in this regard. The common size for magnets, a 3mm Diameter cylinder 1mm tall, has roughly a volume of 7.07mm cubed;
Volume = Pi * Radius(squared) * Height 7.07 = π * 2.25 * 1 A magnet 4mm in diameter and 2mm tall (if you were to apply a .5mm coating) has a volume of 25.13mm cubed;
25.14 = π * 4 * 2 Applying that .5mm coating to a 3mm by 1mm cylinder reduces the volume of magnetic material down to less than 30% of it's volume, which DRAMATICALLY reduces the magnet's strength to a fraction of it's size.
A larger magnet, such as a Rod 3mm in diameter by 6mm tall has a volume of 42.41 cubic millimeters, versus a total coated volume of 87.96. This is still a downgrade to roughly 48% of it's total volume being magnetic, which while still is a huge loss, is a lot more retained strength than the 3mm by 1mm flat disc.
This also demonstrates that coating thicknesses are important. More on this below.
What are these rocks made of?
'Neodymium (NdFeB)' - https://en.wikipedia.org/wiki/Neodymium_magnet
By far the most common, most ideal base composition of magnets. Neodymium boasts the highest magnetic flux density (Gauss) rating among all other magnets, with a maximum rating of N52. Gauss strength is very stable, and will not break down for well over hundreds of years, provided the magnet is not corroded, damaged or otherwise compromised. (And you will have worse things to worry about, anyways). NdFeB magnets can possess anything up to an N52 rating; they are not all automaticially N52. Anything below this rating will not possess the full Gauss capacity, and can be considered inferior. There is very little reason to pursue starting with a magnet rated at say, N42, just don't do it. An n42 has about 80% of the gauss strength of a N52; that 20% is important.
The composition of Neodymium, Iron, and Boron is Toxic to the body. Your body can break it down, if exposed raw, and subject the body to heavy metal poisoning… Which is bad.
NdFeB is very heat sensitive over many other magnets; It CANNOT be autoclaved. Exposure to temperatures roughly above 150°C will begin to damage Gauss strength, which reduces efficiency, and makes it a rock. It is not the easiest material to machine or shape. One reason the Cylinder is so ideal is because it is easy to manufacture (say over, an ellipsoid) correctly.
The majority of NdFeB magnets have a Nickel (technically Ni-Cu-Ni layering)plating over them to prevent the magnet's innards from reacting with the air, and give a degree of mechanical protection from shattering or chipping. They MUST have some kind of coating to protect it from this, and most NdFeB magnets, even WITH alternate coatings (such as Au, TiN, ETC.) Also have a Nickel coating under it, as the NdFeB manufacturer usually isn't also applying a second coating over it.
Almost every magnet implanted is of this variety.
'Samarium Cobalt (SmCo)' - https://en.wikipedia.org/wiki/Samarium%E2%80%93cobalt_magnet
SmCo magnets are rare earth magnets that act similarly to NdFeB magnets in relationship to being
rare earth magnets, and shares it's lifespan of much longer than necessary for human use.
SmCo explores much larger heat boundaries, able to withstand much higher temperature ranges than NdFeB, but also has a lower Gauss capacity than NdFeB magnets, Maxing out at roughly N26.
It's more ideal to simply go with NdFeB.
'Iron Nitride (FeN)' - https://en.wikipedia.org/wiki/Iron_nitride
FeN is a holy grail of magnets, with one of it's nitrides, Fe16N2, being able to pull a theoretical 132N, which would completely shame any NdFeB magnet, and allow for extremely powerful magnets.
Characteristics are somewhat vague, not being an option to the public. As of the time of this writing, The University of Minnesota seems to be the one playing around with this. It's not open for access to play with or explore, unfortunately.
'AlNiCo/Ferrite/Composite'…
Why are you even considering this? No.
Neodymium is toxic, not just Bioincompatible. It will reject. As will the Nickel coating used to protect it (with people having Ni allergies suffering much worse). In fact, most materials in the human body will cause rejection or negatively interfere.
What should be understood about coatings:
Coatings NEED to make the implant, magnet or otherwise, safe in vivo. So the body can't react with it and cause damage to the implant, or worse, itself. A coating ideally needs to be, for the purpose of a magnet, as thin as possible, so as to offer as little inert material as possible and reduce efficiency. A coating should also ideally have a coating that has some degree of rigid strength, to some degree, so as to survive the unlikely but possible mechanical trauma associated. It has no need to flex or give. Coatings have their own page here: http://wiki.biohack.me/Coatings
*PLEASE NOTE*
NEITHER SUGRU NOR HOT GLUE ARE ACCEPTABLE FOR DIY MAGNET PRODUCTION. DO NOT DO THIS. EVER.
http://wiki.biohack.me/Hot_Glue http://wiki.biohack.me/Sugru
Some information extracted here refers directly to the source of which is sold, and should be updated/augmented/considered in accordance. m31 - The m31 is the 'gold standard'. These are 3mm diameter, 1mm tall cylindrical NdFeB magnet, rated at N52 gauss strength. TiN coatings. Very high responsiveness, great sensitivity.
New m31's can be found here, at one point or another: https://dangerousthings.com/ https://cyberise.me/ m36 - The m36 (Really named the m63) is a cylindrical magnet 3mm in diameter, 6mm long. These have about 50% more strength than an m31, and while aren't as responsive for sensing, are ideal for magnetic lifting and suspension. Same TiN coating.
New m36's can be found here, at one point or another: https://dangerousthings.com/ Haworth (silver) - Steve Haworth's magnets are NdFeB magnets, rated at N52, cylinder measured at approximately 3mm around by 1.6mm tall (1/8“ by 1/16”). Parylene coating with Au layer underneath.
Haworth's magnets can be found here, at one point or another: https://steve-haworth-modified-llc.myshopify.com/ Magician's magnet - Another of Steve Haworth's magnets. N52 rated cylinder measuring .3 inches in diameter by .1 inches tall (7.6mm x 2.5mm). Parylene coating with Au layer underneath.
The Magician's Magnet can be found here, at one point or another: https://steve-haworth-modified-llc.myshopify.com/ DIY MAGNETS TO COAT: Fancy to take a stab at it yourself? Here's a good place to get started with 'Raw' magnets:
3x1mm Gold Plated Magnet http://www.gaussboys.com/store/index.php/d04010g-n52.html 4x1mm Gold Plated Magnet: http://www.gaussboys.com/store/index.php/d04010g-n52.html These magnets, however, are not completely safe for implant without additional coating. Coating can be done with gold, rhodium, silver, parylene, and many others. See the coatings page for more information.