Novel physics arising from phase transitions in biology

TL;DR

This paper reviews how phase transitions in biological systems differ from traditional physical ones, highlighting the roles of driven reactions and motility in creating unique behaviors and universality classes.

Contribution

It introduces the concept of novel physics in biological phase transitions, emphasizing driven reactions and motility effects on phase separation and symmetry breaking.

Findings

Driven chemical reactions arrest coarsening kinetics.

Motility leads to a new universality class.

Biological phase transitions differ from thermal systems.

Abstract

Phase transitions, such as the freezing of water and the magnetisation of a ferromagnet upon lowering the ambient temperature, are familiar physical phenomena. Interestingly, such a collective change of behaviour at a phase transition is also of importance to living systems. From cytoplasmic organisation inside a cell to the collective migration of cell tissue during organismal development and wound healing, phase transitions have emerged as key mechanisms underlying many crucial biological processes. However, a living system is fundamentally different from a thermal system, with driven chemical reactions (e.g., metabolism) and motility being two hallmarks of its nonequilibrium nature. In this review, we will discuss how driven chemical reactions can arrest universal coarsening kinetics expected from thermal phase separation, and how motility leads to the emergence of a novel universality class when the rotational symmetry is spontaneously broken in an incompressible fluid.