Scientists at the University of Konstanz have identified a new type of sliding friction that occurs without physical contact, driven by magnetic interactions. This phenomenon breaks Amontons' law, a 300-year-old physics principle, by showing friction peaks at certain distances rather than increasing steadily with load. The findings appear in Nature Materials.
Researchers at the University of Konstanz conducted a tabletop experiment using a two-dimensional array of freely rotating magnetic elements positioned above a second magnetic layer. The layers never physically touch, yet magnetic interactions produce measurable friction during sliding motion. By varying the distance between layers, the team controlled the effective load and observed changes in magnetic structure. Friction proved lowest when layers were very close or far apart, but rose sharply at intermediate distances due to competing magnetic preferences: the upper layer favoring antiparallel alignment and the lower preferring parallel. This conflict causes constant reorientations in a hysteretic manner, increasing energy loss and creating a friction peak, violating Amontons' law—which typically links friction linearly to pressing force via surface deformations. Amontons' law has held for over 300 years based on everyday observations like heavier objects being harder to push. However, in magnetic systems, motion triggers internal rearrangements not accounted for in traditional models. Hongri Gu, who performed the experiments, stated: 'By changing the distance between the magnetic layers, we could drive the system into a regime of competing interactions where the rotors constantly reorganize as they slide.' Anton Lüders, who developed the theoretical model, noted: 'From a theoretical perspective, this system is remarkable because friction does not originate from a physical surface contact, but from the collective dynamics of magnetic moments.' Clemens Bechinger, the project supervisor, added: 'What is remarkable is that friction here arises entirely from internal reorganization. There is no wear, no surface roughness and no direct contact. Dissipation is generated solely by collective magnetic rearrangements.' The physics, independent of scale, may apply to atomically thin magnetic materials. Potential applications include tunable friction for frictional metamaterials, adaptive damping systems, micro and nanoelectromechanical systems, magnetic bearings, and vibration isolation. The study, by Hongri Gu, Anton Lüders, and Clemens Bechinger, was published in Nature Materials (DOI: 10.1038/s41563-026-02538-1).
