Brownian motors are nano-scale or molecular devices by which thermally activated processes (chemical reactions) are controlled and used to generate directed motion in space and to do mechanical or electrical work. These tiny engines operate in an environment where viscosity dominates inertia, and where thermal noise makes moving in a specific direction as difficult as walking in a hurricane: the forces impelling these motors in the desired direction are minuscule in comparison with the random forces exerted by the environment. Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. The vis insita or innate force of matter is a power of resisting by which every body as much as in it lies endeavors to preserve in its present state whether it be of rest or of moving Johnson–Nyquist noise ( thermal noise, Johnson noise, or Nyquist noise) is the electronic noise generated by the thermal agitation Because this type of motor is so strongly dependent on random thermal noise, Brownian motors are feasible only at the nanometer scale.
In biology, many protein-based molecular motors in the cell may in fact be Brownian motors. Molecular motors are biological Molecular machines that are the essential agents of movement in living organisms These molecular motors convert the chemical energy present in ATP into mechanical energy. Adenosine-5'-triphosphate ( ATP) is a multifunctional Nucleotide that is most important as a " molecular currency" of intracellular Energy One example of a Brownian motor would be an ATPase motor that hydrolyzes ATP to generate fluctuating anisotropic energetic potentials. The anisotropic potentials along the path would bias the motion of a particle (like an ion or polypeptide); the result would essentially be diffusion of a particle whose net motion is strongly biased in one direction. The translocation of the particle would only be loosely coupled to hydrolysis of ATP. Loose coupling describes a resilient relationship between two or more systems or organizations with some kind of exchange relationship
The dynamics and activity of Brownian motors are current topics of study in theoretical and experimental biophysics. Biophysics (also biological physics) is an Interdisciplinary Science that employs and develops theories and methods of the Physical sciences for Brownian motors are sometimes modeled using the Fokker-Planck equation or with Monte Carlo methods. The Fokker–Planck equation describes the Time evolution of the Probability density function of the position of a particle and can be generalized to other observables Monte Carlo methods are a class of Computational Algorithms that rely on repeated Random sampling to compute their results Many researchers are presently engaged in understanding how molecular-scale motors operate in environments with non-negligible thermal noise. The thermodynamics of such motors is constrained by the ramifications of the Fluctuation Theorems. The fluctuation theorem (FT is a theorem from Statistical mechanics dealing with the relative probability that the Entropy of a system which is currently away from
See also
External articles
- R. The Brownian ratchet is a Thought experiment about an apparent Perpetual motion machine conceived by Richard Feynman in a Physics lecture at This article is about the physical phenomenon for the stochastic process see Wiener process. The fluctuation theorem (FT is a theorem from Statistical mechanics dealing with the relative probability that the Entropy of a system which is currently away from Robert Brown FRS ( 21 December, 1773 &ndash 10 June, 1858) was a Scottish scientist who is acknowledged as the leading botanist D. Astumian (1997). "Thermodynamics and kinetics of a Brownian motor", Science 276, p. 917-922.
- J. A. Freund, T. Pöschel, ed. (2000). Stochastic processes in physics, chemistry, and biology. Lecture notes in physics, vol. 557. Springer Publishers, Berlin.
- Lukasz Machura: Performance of Brownian Motors. University of Augsburg, 2006 (PDF)
- Brownian motor on arxiv.org
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