Microtribology

Microtribology is the study of friction, wear, and lubrication at micro- to nanoscale interfaces. It focuses on how surface forces and contact mechanics differ at small scales from those observed in bulk contacts, driven by high surface-to-volume ratios, adhesion, capillary and electrostatic forces, and the elastic or plastic response of materials in tiny contact areas.

It covers phenomena such as adhesion-controlled contact, size effects, and tribochemical reactions that can alter surface chemistry during sliding. Friction at these scales is influenced by the presence or absence of lubricants, boundary films, and the transition between boundary, mixed, and hydrodynamic lubrication regimes. At micro scales, capillary and electrostatic forces become significant and can dominate friction and wear, particularly in humid environments.

Measurement and characterization rely on specialized tools: atomic force microscopy and lateral or friction force microscopy measure nanoscale friction forces; nanoindentation assesses mechanical response; micro-tribometers and MEMS test rigs evaluate sliding behavior under controlled conditions.

Applications include MEMS and NEMS devices where stiction, adhesion, and wear limit performance; data storage heads; micro-robotics; and any application requiring reliable, low-friction interfaces at small scales. Materials and coatings such as diamond-like carbon, graphene, and ultrathin lubricant films are explored to reduce wear and energy loss.

Challenges include reproducing macro-scale lubrication behavior at micro scales, controlling environmental effects such as humidity, wear debris generation, and bridging the gap between fundamental measurements and device-level reliability. Ongoing research seeks to understand and exploit phenomena such as superlubricity and tribochemistry to extend nanoscale lifetimes.