Bearings play a crucial role in many sorts of machinery
Machines with moving parts must have some way to link those parts and guide their motions. Although parts sometimes move solely by bending or stepping, their interfaces more commonly allow turning, sliding, or rolling motions. Structures that enable such motions are often termed bearings.
Biomechanical systems on all scales make extensive use of bending and stepping motions. For example, our legs bend in order to step, and their muscles are powered by myosin molecules [w/animation] that do likewise. Nonetheless, even these motions involve bearings for example, sliding cartilage in skeletal joints at the macroscale and twisting bonds in molecules at the nanoscale. Biology, which notoriously lacks rotary parts at the macroscale, employs them at the molecular scale (e.g., the bacterial flagellar motor and the driveshaft-powered ATP synthase complex [MPEG]).
Studies of advanced nanosystems suggest that nanoscale productive systems can make use of machines similar in organization and structure to those found in macroscopic factories. These molecular machine systems typically contain many bearings.
Mobile interfaces and moving parts:
Drexler, KE. (1992) Nanosystems: Molecular Machinery, Manufacturing, and Computation. Wiley/Interscience, pp.273319.