The Mechanistic Integration and Thermodynamic Optimality of a Nanomotor

The performance of artificial nanomotors is still far behind nature-made biomolecular motors. A mechanistic disparity between the two categories exists: artificial motors often rely on a single mechanism to rectify directional motion, but biomotors integrate multiple mechanisms for better performance. This study proposes a design for a motor-track system and shows that by introducing asymmetric compound foot-track interactions, both selective foot detachment and biased foot-track binding arise from the mechanics of the system. The two mechanisms are naturally integrated to promote the motility of the motor towards being unidirectional, while each mechanism alone only achieves 50% directional fidelity at most. Based on a reported theory, the optimization of the motor is conducted via maximizing the directional fidelity. Along the optimization, the directional fidelity of the motor is raised by parameters that concentrate more energy on driving selective-foot detachment and biased binding, which in turn promotes work production due to the two energies converting to work via a load attached. However, the speed of the motor can drop significantly after the optimization because of energetic competition between speed and directional fidelity, which causes a speed-directional fidelity tradeoff. As a case study, these results test thermodynamic correlation between the performances of a motor and suggest that directional fidelity is an important quantity for motor optimization.