A magnet, re-magnetized as a code.

Maxels: magnetic pixels

A conventional magnet is a dipole — one north face, one south face, a field that loops far into space, and exactly two tricks: attract and repel. A programmable magnet (CMR’s trademark: Polymagnet®) is the same piece of ordinary NdFeB, re-magnetized with a printed pattern of many small N and S regions — maxels, magnetic pixels roughly 1–4 mm across — on a single face.

Neighboring maxels close their flux loops locally, so the field concentrates at the surface and dies fast with distance. For a periodic pattern the falloff is exponential — F ∝ e^−2πz/λ, where λ is the pole pitch. Fine pattern: intense, short-throw (CMR recommends working gaps under 2 mm). Coarse pattern: gentler, longer reach. Reach itself is a design knob.

Correlation: the force curve as signal processing

Larry Fullerton’s insight was to design the pattern like a radar code. Two mating coded surfaces attract according to the spatial correlation of their codes: at exact alignment every maxel pair is complementary and force peaks like a matched filter; off alignment, attractions and repulsions cancel and the force collapses — “typically about an order of magnitude” less, per patent US 7,800,471. The patents used Barker codes; the engineered result is called the spatial force function. Differently coded pairs simply ignore each other: lock-and-key, in physics.

The MagPrinter: a dot-matrix printer for magnetism

Patterns are written by a computer-controlled magnetizing head firing ~0.8 ms current pulses through a ~1 mm aperture — one maxel at a time (writing patents US 10,204,727 and family). Workflow: pick a function from the software catalog or design a custom one, insert a blank magnet, print the pattern in seconds to minutes, force-test. The first MagPrinter shipped in 2013; a desktop Mini MagPrinter followed in 2014 at roughly $45,000.

What coding cannot do

Coding redistributes the material’s magnetic energy; it cannot add any. NdFeB tops out around 52 MGOe whether plain or printed. No free levitation either — Earnshaw’s theorem forbids stable static levitation, and CMR’s own FAQ says so. Every “floating” spring demo runs on a pin.