The geometry-tuned Casimir cell

Why the library suggests it

Jeremy Munday's group measured a single 300-nanometre gold pillar cutting the force by roughly a factor of ten, a pillar with a hole through it bending the force-versus-distance curve the other way, and a dense pillar array nearly tripling the force — all in ordinary air at room temperature (Casimir Force Control Enabled by 3D Nanostructures, 2025). The reason shape rather than energy is the right handle was worked out long before: inside a rectangular cavity the vacuum can push outward on one pair of faces while pulling inward on another at the same time, which is why an energy-only account of a Casimir cycle gives the wrong answer (Unusual properties of conductive rectangular cavities in the zero point electromagnetic field, 1999). Fabrizio Pinto built the apparatus and the calibration procedure for driving something with that force rather than merely measuring it (Membrane actuation by Casimir force manipulation, 2008).

The experiment or build

Take a sphere-and-plate Casimir rig — the standard instrument in the field — and fabricate a plate carrying a library of patterns: bare, single pillar, holed pillar, arrays at several pitches. Measure the force against separation for each. Then close the loop: drive a membrane with the patterned surface and read its resonance. The settling measurement is the force per unit area at a fixed separation, plotted against pattern geometry, with the electrostatic calibration published alongside it — because the calibration is where this measurement is won or lost. Harold White's group found something else while doing exactly this kind of modelling, which is the subject of a later card (Worldline numerics applied to custom Casimir geometry, 2021).