  Biology achieves novel functions like error correction, ultra-sensitivity and
accurate concentration measurement at the expense of free energy through
Maxwell Demon-like mechanisms. The design principles and free energy trade-offs
have been studied for a variety of such mechanisms. In this review, we
emphasize a perspective based on dynamical phases that can explain
commonalities shared by these mechanisms. Dynamical phases are defined by
typical trajectories executed by non-equilibrium systems in the space of
internal states. We find that coexistence of dynamical phases can have dramatic
consequences for function vs free energy cost trade-offs. Dynamical phases can
also provide an intuitive picture of the design principles behind such
biological Maxwell Demons.
