Ultralowfriction

Ultralowfriction refers to tribological systems in which the friction between contacting surfaces is exceptionally small, often approaching regimes described as superlubricity. The term covers phenomena observed at nanoscale interfaces as well as engineered macroscopic contacts, where the effective coefficient of friction can be significantly lower than in traditional lubricated joints.

Key mechanisms behind ultralow friction include superlubricity arising from incommensurate crystallographic alignment between sliding surfaces, which reduces interfacial shear resistance. Stable lubricating films—whether solid, liquid, or liquid-like layers—can further separate interfaces and minimize adhesion and plowing. Surface engineering, cleanliness, and controlled environmental conditions also play important roles in maintaining low friction.

Materials that have shown promise for ultralow friction include layered or two-dimensional materials such as graphene, hexagonal boron nitride, and other transition metal dichalcogenides. These materials can exhibit low shear strength when clean and properly oriented, especially in combination with appropriate lubricants or surface treatments. Other approaches involve soft or textured surfaces, chemical passivation, and the use of advanced lubricants, including ionic liquids or nanostructured coatings, to sustain low friction under operation.

Applications of ultralow-friction concepts span micro- and nano-scale devices, such as MEMS and precision positioning systems, as well as larger-scale bearings where energy efficiency and wear reduction are important. Challenges include sensitivity to contamination, humidity, load, and wear-driven transitions to higher friction, as well as scaling laboratory demonstrations to practical, durable engineering solutions. Ongoing research seeks to understand fundamental limits, identify robust material systems, and enable reliable, wide-range applications.