Brownian Motion Machine

In 1912, Marian Smoluchowski proposed a prototype for an engine at the molecular scale which he thought could convert Brownian motion into work. It consisted of a series of vanes mounted on an axis and set into motion by molecular bombardment. An asymmetrical cog ensuring that the axis could only rotate in one direction so that the device could perform work such as lifting a weight.

In 1963, Richard Feynman demonstrated that the second law of thermodynamics would prevent the device from working in a system that was in a state of thermal equilibrium.

Scientists from the University of Twente, the University of Patras in Greece and the Foundation for Fundamental Research on Matter (FOM) have now demonstrated the first working Brownian Motion engine. Using a granular gas, a solid suspended in air that is constantly vibrated, a constant supply of energy is required to maintain the granular gaseous state so that the system is never at thermal equilibrium. Once the vanes of the engine start rotating, they induce a rotating motion in the gas known as a convection roll, which reinforces the movement of the device and allows for virtually continuous rotation.

Reference:
Peter Eshuis, Ko van der Weele, Detlef Lohse and Devaraj van der Meer. Experimental Realization of a Rotational Ratchet in a Granular Gas. Phys. Rev. Lett., 104, 248001 (2010) DOI: 10.1103/PhysRevLett.104.248001

Study Questions:

1. What is brownian motion?
2. What are the three laws of thermodynamics?
3. What is meant by term thermal equilibrium?
   
4. Why would the second law of thermodynamics prevent this device from working in a system that was at thermal equilibrium?
5. List the ways in which a granular gas is similar to compound in the gaseous state.
6. List the ways in which a granular gas is different to a compound in the gaseous state.