Casimir Force Control Enabled by 3D Nanostructures

The Casimir force dominates interactions between solid objects at sub-micrometer distances and typically limits the smallest distance between micromechanical devices before failure. Here, we experimentally circumvent this limitation by controlling the Casimir force with engineered 3D nanostructures. Using our recently developed method to align and measure the force between two microscale objects on the nanoscale, we characterized the force gradient between spheres and circular pillars, hollow cylinders, and periodic pillar arrays. We demonstrate that the force behavior can be dramatically modified in these geometries, resulting in a suppression of the Casimir force by 10× for a single pillar. We found agreement between theory and experiment, even when the size of the objects was comparable to the surface-to-surface separation (i.e., within a factor of ∼3). We anticipate that our results will impact the design of future micro- and nanoscale actuators, optomechanical devices with increased sensitivities and reduced stiction, and advanced bio-inspired adhesives.