Magnets. They work because electrons like being in spin pairs.
In Huntsville, Alabama, a company called Polymagnet is “printing” magnets with properties never quite seen before.
Destin Sandlin from the YouTube channel Smarter Every Day interviewed the company's engineers in March and was given an extensive tour. What he found amazed him:
Magnets four times stronger than average but made using the same ordinary materials. Magnets that attract until they are a centimeter away and then repel (which Polymagnet calls "springs"). Magnets that repel until you give them a quarter-turn (like a key) and then they snap together with immense force for no obvious reason.
To understand how that can be, consider a hard drive platter (the old “spinning rust” kind, not the newer solid state drives). Imagine you wrote a random pattern of bits represented by north and south poles across the whole surface of the disk.
Now imagine you wrote its exact mirrored pattern on a second platter, swapping right to left and north to south. Those two disk platters would attract, but only when they were aligned correctly, face to face.
If you turned one enough to break the alignment, the platters won’t be nearly as attracted. They might even repel if you wrote the correct pattern. You just have to do the combinatorial math, and remember you’re dealing with space-filling fields that greatly depend on distance.
Polymagnet has applied this concept at full power with their “correlated magnetics”.
A blank form goes into their 3D-printer-like machines and they write “magnetic pixels” (or "maxel", if you will) to it under careful software control.
Printed "maxels" creating complementary, mirrored halves.
The exact properties of the magnetic field can be tuned so that it has the desired shape and mechanical feel, such as laptop hinges or phone holders that lock firmly at particular angles. How 'firmly' can be carefully tuned by the designers by writing a customized magnet.
But Polymagnet can produce more than just magnets with finesse… they can also create brute force.
By closely alternating the poles over the surface of their printed magnets, they can tighten the field loops so less is wasted on free space. Essentially, a Halbach array made from a single piece of material instead of the difficult and often dangerous stacking of smaller magnets together.
Illustration of the different field loops between conventional and Polymagnet magnets.
Magnetic viewing film reveals the intricate patterns Polymagnet is capable of printing:
Here's the turn-key style "latch" design, compared to a conventional magnet:
Magnetic viewing film over a conventional magnet (top) and a printed latching magnet (bottom).
Polymagnet has individual samples of their latches and springs available for experimentation—or for confusing your engineer friends.
All images and gifs courtesy of Destin Sandlin. Subscribe to his channel at Smarter Every Day.