  While the dependence of the directed transport on each of the
ratchet-controlling parameters has been individually investigated
experimentally, theoretically, and numerically, there is still no general
criterion to apply to the whole set of these parameters to optimally control
directed transport in general systems. We report that, to optimally enhance
directed transport, there exists a universal force waveform which can be
understood as the result of two competing fundamental mechanisms: the increase
of the degree of breaking of symmetries and the decrease of the force impulse.
We demonstrate that this universal waveform explains all the previous
experimental, theoretical, and numerical results for a great diversity of
systems, including motor enzymes.
