title: Directional fidelity of nanoscale motors and particles is limited by the 2nd law of thermodynamics--via a universal equality.
abstract: Directional motion of nanoscale motors and driven particles in an isothermal environment costs a finite amount of energy despite zero work as decreed by the 2nd law, but quantifying this general limit remains difficult. Here we derive a universal equality linking directional fidelity of an arbitrary nanoscale object to the least possible energy driving it. The fidelity-energy equality depends on the environmental temperature alone; any lower energy would violate the 2nd law in a thought experiment. Real experimental proof for the equality comes from force-induced motion of biological nanomotors by three independent groups - for translational as well as rotational motion. Interestingly, the natural self-propelled motion of a biological nanomotor (F1-ATPase) known to have nearly 100% energy efficiency evidently pays the 2nd law decreed least energy cost for direction production.
authors.affiliation: Department of Physics, National University of Singapore, Singapore 117542. phywangz@nus.edu.sg
authors.forename: Zhisong
authors.initials: Z
authors.lastname: Wang
authors.forename: Ruizheng
authors.initials: R
authors.lastname: Hou
authors.forename: Artem
authors.initials: A
authors.lastname: Efremov