In one minute

Spreng and colleagues start from the fact that the Casimir interaction between dielectric objects in salty water contains a universal part the solvent does not screen, so it reaches over long distances. That non-screened universal force has already been measured experimentally, on a microsphere held by optical tweezers next to a larger fixed sphere. They derive the Casimir free energy for two parallel dielectric cylinders with the scattering method. Its magnitude far exceeds the thermal energy scale over a wide range, including the sizes of actin filaments and microtubules in cells. At every distance of biological interest the free energy depends only on geometry, not on the cylinders' dielectric response. This universal attraction should help hold bundles of parallel filaments together.

Universal Casimir attraction between filaments at the cell scale