Transmission of torque at small scales: the nanoclutch
6 October 2015
A model microscopic system to demonstrate the transmission of torque in the presence of thermal fluctuations – necessary for the creation of a tiny 'clutch' operating at the nanoscale – has been assembled at the University of Bristol as part of an international collaboration.
When driving a car, the clutch mechanically carries the torque produced by the engine to the chassis of the vehicle – a coupling that has long been tested and optimized in such macroscopic machines, giving us highly efficient engines. For microscopic machines, however, developing a clutch which would operate at the nanoscale is much more challenging because, at microscopic length scales, different physics need to be considered. Thermal fluctuations play an increasingly dominant role as a device is miniaturised, leading to increased dissipation of energy and the need to develop new design principles.
In the model microscopic system developed by scientists from Bristol, Düsseldorf, Mainz, Princeton and Santa Barbara, a ring of colloidal particles are localised in optical tweezers and automatically translated on a circular path, transferring a rotational motion to an assembly of identical colloids confined to the interior region.
Dr Paddy Royall of the University of Bristol said: “This device looks a lot like a washing machine, but the dimensions are tiny. Through optical manipulation the particle ring can be squeezed at will, altering the coupling between the driven and loaded parts of the assembly and providing a clutch-like operation mode.”