From vortex ratchets to rectification of self-propelled swimmers

During the last decades, the mastering of flux quanta in superconductors has received a growing attention in the scientific community due to the large spectrum of possible analogies between fluxon physics and other apparently disconnected topics. For instance, flux avalanches in superconducting thin films resemble the crack propagation in solids or the electrical discharges during dielectric breakdown, whereas a flux lattice interacting with a periodic substrate could be thought of as a model of charge-density-waves.
Among the most remarkable achievements of flux control we find the flux ratchets, a mechanism allowing to obtain average flux motion along a predefined direction with zero-mean excitations. This is a basic element for the development of more complex devices such as flux pumps and magnetic flux lenses. In this talk, I will show how the concepts of flux rectification has been extended to self-propelled particles, such as human sperm cells population, for which it is not necessary an external power supply to achieve separation, concentration or sorting of particles.