Multi-level magnetism
Most people think of a magnet as having one behavior. Two magnets either attract or repel. Polymagnets broke that assumption years ago with spring, latch, and alignment functions. Multi-level magnetism goes further. A single Polymagnet pair can switch between attract and repel at a prescribed distance. The result is two or more distinct force levels within one magnetic interaction.
We consider this one of the most important capabilities in our technology. It enables behaviors that no conventional magnet can produce and that most engineers don’t even know to ask for.
The concept of force levels
A conventional magnet pair has a single force curve. Pull them apart, and the force weakens in a smooth, predictable decay. Push them together in repel orientation, and the force grows in a smooth, predictable rise. One curve. Single behavior.
Multi-level Polymagnets produce a force curve with inflection points. The force may be repulsive at close range and attractive further away, or the reverse. A specific separation distance marks the transition between modes. We call that distance the transition point, and it is adjustable through the maxel code.
Two levels is the simplest configuration: a repel zone and an attract zone. A pair coded for this behavior will push apart at close proximity, then switch to attraction at a defined distance. The magnets settle at an equilibrium between the two forces. This is the principle behind our HoverField products, where two magnets float at a prescribed separation without contact.
More advanced configurations have three or more levels. A three-level code might attract at long range, repel at mid-range, and attract again at close range. Such a force curve has two inflection points and produces a “snap through” behavior. The magnets attract, resist at a mid-range barrier, and then snap together when pushed past it.
How multi-level behavior is encoded
Each Polymagnet in a multi-level pair has two distinct magnetic regions printed on the same surface. We refer to these as the short-range component and the long-range component.
The short-range component is a dense maxel arrangement with high spatial frequency. It creates a strong near-field force that decays fast with distance. A few millimeters away, the short-range field is dominant. One centimeter out, it’s negligible.
Its counterpart, the long-range component, uses a lower-frequency arrangement. Often a single large pole or a small number of wide maxels. Its field extends further but produces a weaker peak force. Close up, the short-range field overwhelms it. Further out, it’s the only force present.
We tune the relative strength of these two components by adjusting maxel amplitude during the print process. Our MagPrinter induction coil can vary the input power for each maxel. Higher power produces a stronger saturation. Lower power produces a weaker one. The ratio between the two components determines where the transition occurs and how abrupt the mode change is.
This is not two separate magnets stacked together. Both components exist on the same surface of the same piece of magnetic material, printed in a single pass. The magnet looks identical to any other Polymagnet from the outside. Multi-level behavior is embedded in the code.
Transition point control
The transition point is the most critical parameter in a multi-level design. It defines the distance at which force crosses zero and switches direction. Below it, one mode dominates. Above it, the other takes over.
We can set the transition point from less than a millimeter to several millimeters, depending on magnet size, material grade, and maxel configuration. Larger magnets with higher-grade neodymium allow a wider transition range. A small ferrite magnet will have a narrower range, but the multi-level effect is still achievable.
The rate of transition is adjustable too. A steep transition creates a crisp boundary between the two force levels. The magnet snaps from one mode to the other with very little dead zone. A gradual transition produces a softer changeover with a broad region of near-zero force between levels.
Product designers can specify both the transition distance and the transition rate as part of the design process. Our engineering team models the force curve before printing and validates it against specifications after.
Stacked multi-level structures
Some applications need more than two levels or more than two magnets. We’ve developed stacked multi-level assemblies that use three or more Polymagnets in series for complex sequential behaviors.
One example is a click-on/click-off assembly. Three magnets are arranged in a stack. The top and bottom magnets are coded to interact with the middle magnet in a repel-snap configuration. A force applied to the top magnet pushes the middle magnet down until it snaps to the bottom. The next press disengages the bottom pair and re-engages the top pair.
No mechanical spring or detent ball is involved. The toggle is entirely magnetic, and the two stable states are defined by the code. Cycle life is indefinite because magnets don’t wear.
Another use case is a linear multi-position detent. Multiple Polymagnets are arranged along a rail. A sliding magnet locks into discrete positions defined by multi-level codes at each station. The slider resists displacement between stations and snaps into the next position when pushed past the transition barrier. Position count, holding force at each station, and the force required to shift between them are all specified in software.
Applications
Multi-level magnetism has entered production in several product categories:
- Contactless suspension. Hovering fixtures for sensitive instruments, vibration-isolated platforms, and clean-room equipment where surface contact introduces contamination
- Magnetic closures. Enclosures that resist opening up to a defined force, then release when that force is exceeded
- Sequential latching. Multi-state toggle mechanisms that switch between two or more locked positions without springs or cams
- Overload protection. Couplings that hold under normal load and disengage at a defined threshold without damage to connected components
- Child safety closures. Magnetic latches where the transition barrier exceeds a child’s strength but remains accessible to an adult
We’ve also explored multi-level magnetism for anti-counterfeiting. A product coded with a specific multi-level force profile can be verified using a test fixture that measures the force curve. Counterfeit products using conventional magnets will produce a different curve. The force profile is a magnetic signature that’s difficult to replicate without our MagPrinter and the correct code. We’ve tested this with a consumer electronics OEM and confirmed that the force signature can distinguish authentic product from counterfeit.
How we develop multi-level codes
Every multi-level Polymagnet is defined in software. Our Polyvision design tool lets engineers visualize the force curve before printing. The software displays the predicted transition point, peak force levels, and equilibrium distance. Changes to the maxel code update the curve prediction in seconds.
We can print a multi-level pair, measure the force curve, compare it to the prediction, adjust the code, and reprint within one working day. Most multi-level designs converge in two or three iterations. The transition point is reproducible across production volumes because our MagPrinter controls every maxel.
Multi-level Polymagnets are available in neodymium, samarium cobalt, ferrite, and flexible magnetic stock. Size and geometry constraints are the same as for any other Polymagnet in our catalog. The multi-level capability is a function of the code.