Experimental realization of Feynman's ratchet

• Published in: New journal of physics Vol. 20; no. 10; pp. 103032 - 103038
• Main Authors: Bang, Jaehoon, Pan, Rui, Hoang, Thai M, Ahn, Jonghoon, Jarzynski, Christopher, Quan, H T, Li, Tongcang
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 25-10-2018
• Subjects: Algorithms; Brownian ratchet; Data processing; ENGINEERING; Feedback control; Feynman's ratchet; Heat engines; Molecular motors; non-equilibrium thermodynamics; optical tweezers; Physics; Reservoirs; Stability; Temperature gradients; Thermodynamic equilibrium; Thermodynamics; Variation
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/aae71f

Feynman's ratchet is a microscopic machine in contact with two heat reservoirs, at temperatures TA and TB, that was proposed by Richard Feynman to illustrate the second law of thermodynamics. In equilibrium (TA = TB), thermal fluctuations prevent the ratchet from generating directed motion. When the ratchet is maintained away from equilibrium by a temperature difference ( T A T B ), it can operate as a heat engine, rectifying thermal fluctuations to perform work. While it has attracted much interest, the operation of Feynman's ratchet as a heat engine has not been realized experimentally, due to technical challenges. In this work, we realize Feynman's ratchet with a colloidal particle in a one-dimensional optical trap in contact with two heat reservoirs: one is the surrounding water, while the effect of the other reservoir is generated by a novel feedback mechanism, using the Metropolis algorithm to impose detailed balance. We verify that the system does not produce work when TA = TB, and that it becomes a microscopic heat engine when T A T B . We analyze work, heat and entropy production as functions of the temperature difference and external load. Our experimental realization of Feynman's ratchet and the Metropolis algorithm can also be used to study the thermodynamics of feedback control and information processing, the working mechanism of molecular motors, and controllable particle transportation.