The Casimir force is a quantum-mechanical interaction arising from vacuum fluctuations of the electromagnetic (EM) field and is technologically significant in micro- and nanomechanical systems. Despite rapid progress in nanophotonics, the goal of engineering this force remains elusive, as many complex EM modes over a broad energy scale contribute simultaneously. Here we nanostructured one of two interacting gold surfaces into a high aspect ratio lamellar grating with 100 nm features. For inter-surface separation distances d above ≈ 400 nm, the measured Casimir force in vacuum decreases faster than the d^-4 power-law, reducing by up to a factor of 2 compared to the prediction of the proximity force approximation, valid for planar-like geometries. The strong force suppression, in agreement with our numerical analysis, is inconsistent with either perfect electrical conductivity or an effective medium description, and surface plasmon-like states with evanescent EM fields may play an important role. This work opens new possibilities for control of this fluctuation-induced interaction via material properties and geometric structure.
Citation: Nature Communications
Pub Type: Journals
Casimir force, nanofabrication, nanostructure, vacuum fluctuations, plasmons, force measurement, MEMS, NEMS, microelectromechanical, nanoelectromechanical, e-beam, electroplating