Ryo Kanada

Thermal ratchets with symmetric potentials

It is shown that the directed transport of Brownian particles can be induced by thermal ratchets with symmetric, two-state fluctuating potentials, contorary to an earlier belief that at least three states are needed for the potential to fluctuate if the potential is symmetric. It is proved that the potential must lack the symmetry of glide reflection in order for the directed movement of particles to occur in a two-state ratchet. Based on this finding, several models with symmetric potentials are constructed to demonstrate the occurrence of the particle flow.

Efficiency of Energy Transduction in a Molecular Chemical Engine

A simple model of the two-state ratchet type is proposed for molecular chemical engines that convert chemical free energy into mechanical work and vice versa. The engine works by catalyzing a chemical reaction and turning a rotor. Analytical expressions are obtained for the dependences of rotation and reaction rates on the concentrations of reactant and product molecules, from which the performance of the engine is analyzed. In particular, the efficiency of energy transduction is discussed in some detail.