PHYSICISTS have worked out a way to create “negative friction”, where molecules speed up as they pass each other instead of slowing down. Mastery of the effect and others like it could help in the design of microscopic machines and reveal how biomolecules interact within cells.
Key to the effect are van der Waals forces, which normally cause molecules to attract each other weakly. Electrons in the molecules vibrate, causing slightly positive charges in some regions and negative ones in others. If the regions are close together, the positive and negative charges attract each other. This pull gives large molecules…
