Printed Magnets

That is cool....I wonder about the longevity of the integrity...and some actual testing of the field densities...

If I understand correctly, they are not adding anything, so "printing" is really a misnomer. I believe the "printing" process is simply magnetizing tiny regions of the existing stock material with appropriate polarities. What amazes me is their ability to create the very strong and very concentrated fields required to magnetize those tiny regions. The magnetizing field always has to be significantly stronger than the resulting permanent magnet field strength, and as you imply, magnetizing a region of one polarity very close to another of the opposite polarity would seem to partially weaken the prior field, either immediately or over time.

You can obviously magnetize very tiny regions. I've got a Terabyte drive that has about 8 trillion magnetized regions.

Will it be as long-term reliable as 90-minute cassette tapes with noticeable print-through from one layer to the next?

Good point. On the other hand, I have around 20 powder technology magnetic door latches on my kitchen and utility cabinets, that were installed 54 years ago. A couple of the magnets have disintegrated (the binder has presumably decomposed), but the magnetism still holds them together. I have replaced one or two, the rest continue to do their job.

Rubber-based refrigerator magnets commonly have alternating parallel poles a millimeter or two apart. If you place two identical ones back-to-back and rotate them, you will find two angular positions where they have maximum attraction, and they will snap close to that angular position. If you then hold them carefully in that angular position and slowly move them past each other perpendicular to the pole lines, they will alternately attract and repel. For many years, I've been carrying a pair of fake American express card magnets around in my computer bag to illustrate the effect. Here they are in a plastic baggie with some debris picked up near my bench grinder:

That's a millimeter scale along the bottom. If there has been any degradation of the magnet strength, I can't tell.

I've been saving the magnets from dead hard drives for close to 30 years, and they are still very strong. I believe they are closer in composition to the material used for the PolyMagnets than the previous magnetic materials I mentioned.

Finally, like the guy in the video, my dad worked in a Magnavox loudspeaker factory during the 2nd WW, and he too brought some (AlNiCo) magnets home. I played with them starting when I was around 5, and still have at least one of them over 70 years later. Of course they were never even close to the strength of modern rare earth magnets, but they seem to have pretty close to their original strength. Here's part of one (Note the reflections of the scale; after 70+years of handling, the ground surfaces are still polished):

To summarize: With the materials and technology available now, I see no reason why the PolyMagnets should last less than a century, as long as they don't experience frequent large sudden shocks against other magnetic materials.

What's interesting is that refrigerator magnets are strongly magnetic on one side and very weakly on the other, a perfect example of a Halbach array.

https://en.wikipedia.org/wiki/Halbach_array

Right! I have to confess I knew about it, but I'd forgotten both the term and the concept. I'm afraid that kind of occurrence is becoming more common in my 4th quarter century...

I'm in my second quarter and only learned of it moments before the post (from the same wiki article).

I had always wondered why fridge magnets were so weak on one side.

Every day, regardless the weather or one's circumstances, there is knowledge to be gained. What a joy that is.

I have no idea how they are doing it, but one technique might be to use a laser to temporarily heat a spot to the Curie temperature and "freeze" an applied magnetic field in that spot, such as done in a magneto-optical drive.

https://en.wikipedia.org/wiki/Magneto-optical_drive

Pretty clever. Another application might be a magnetic lock, where the matching key would attract a piece inside the lock to open it. No other key would work. (Maybe that's already been invented.)

Decades ago, standard mechanical disc type energy meters were fitted with magnetic levitation bearing to increase its sensitivity at lower power levels. These levitation bearings were basically epoxy bonded multi polar magnets with concentric geometry. What is shown here is complex multi polar magnets with pixel geometry. Instead of hard epoxy (like Araldite) now polymer is being used for bonding. Concept has been known for over decades.

So you think the "printing" process is actually adding little tiny magnets? ...or possibly that the blank is constructed of many separate tiny magnets that are held together by a polymer, and are subsequently magnetized?

I presume (_{there's that dangerous word again}) that the "Poly" of "PolyMagnet" refers to many poles, not to polymers.

I went back and viewed the "printing" process again (near the end of the Smarter Every Day video). The PolyMagnet looks identical before and after "printing", and there was apparently no curing time (although that could have been edited out).

Standard NdFeB magnets are (or at least used to be) pressed from powder under very high pressure, so each particle of the powder can theoretically be magnetized individually. I have the impression that they are taking a blank of some similar material and magnetizing tiny regions with the appropriate polarities. Obviously, I could be mistaken...

No, I think you are spot-on.

Thanks for posting this. I think that this concept will soon be showing up in a plethora (I just watched "The Three Amigos" again, and am using that word every chance I get!) of industrial and domestic applications.

I did not see the process. But I was working with a energy meter company and these multi polar levitation magnets were made by a sister concern. So had discussed the process to under it better. My understanding is they used to get (then Neodymium magnets were unknown) hard ferrite powders. It was mixed with epoxy. Then it is pressed to what ever shape is needed. It is during pressing time and curing, they had permanent magnet jigs with specific alignment. So you can say- under green or wet condition these magnetic powders are still free to move and align under influence of external magnetic flux. After the epoxy hardens pole shape cannot be changed. Then the poles can be induced by applying current through external coils etc. Magnets are formed in situ. You DO NOT START WITH MAGNETS. Input is just a hard ferrite powder (it could be Strontium hard ferrite magnetic material powder)+ epoxy or polymer in this case.

I've been magnetizing magnets off and on since the early '60s (and on a personal scale since the mid '40's). At that time it was for both military and domestic magnetrons. We regularly changed the magnetic field strength of large permanent magnets (weighing anywhere from less than a pound up to several hundred pounds), to find the optimum field strength for the particular application, by applying very short pulses of incredibly large magnetic fields. One of our magnetizing machines used a single-turn secondary of a transformer having around 3 square inches of copper, carrying a current pulse on the order of 100kA. If the magnetizing field had the same polarity as that of the permanent magnet, and had sufficient strength, it would increase the strength of the permanent magnet. If it had the opposite polarity, it would either weaken the permanent magnet, or reverse its polarity, depending on the strength of the magnetizing field.

Clearly, magnetic hard drives do the same thing on a vastly smaller scale.

I believe the PolyMagnets use the same principles at an intermediate scale.

There is no need for the magnetizable material to actually change position while being magnetized, as long as the magnetizing field is sufficiently strong to overcome the previous orientation, if any, of the existing magnetic domains.

I appreciate your expertise in this field. Yes , polymer magnets cannot be very different as discussed here. I have seen huge magnetizing presses about 40 to 50 feet tall in which many magnets were being magnetized by this kind of pulses. 50 Amps through a 100 turns water cooled coil. It was for making magnets for auto sector magnetos. Many ferrite magnets being placed- in green condition.

But what is being shown here seem to be powerful strontium or neodymium magnets. Concepts are same.