Dear Trishit,

  of course it exists, if not, we wouldn't have the engines of cars that convert a part of the kinetic Brownian energy of molecules into mechanical energy. The problem is that you can't do so without increasing the entropy of the whole system (second principle of thermodynamic). In other words it doesn’t exist a mechanism (thermodynamic cycle) whose only effect is to convert Brownian motion energy (heat) in mechanical energy. You could expand a system in an isentropic way, to convert his Brownian motion in linear motion, however this is not "a way", but only a thermodynamical transformation.

Cheers,

Francesco

Basically not possible, except that the motion is at scales even smaller than the free path!