Order from chaos: How physics explains the secrets of life’s self-organising pattern
A research team from CUHK’s Department of Physics observes that living fluids consisting of bacteria produce a regular vortex pattern in turbulence with multiscale order (image shows the experimental data). This simple new physical mechanism is called ‘self-enhanced mobility’.
Leading physicists from CUHK have hit upon a breakthrough discovery that sheds new light on how living matter spontaneously forms into the self-organised structures that bring order to our world. The finding has the potential to drive innovation in regenerative medicine, biologically inspired materials, and self-propelled nanotechnology devices. The result has recently been published in the scientific journal Nature.
The orderly functioning of living systems depends on a host of self-organised structures operating at various scales: everything from cells, tissues, organs and organ systems, to organisms, populations, communities and ecosystems. Self-organised, ordered spatial structures formed by the aggregation of cells also play vital physiological functions, such as the development of embryos.
To date, the emergence of such structures has generally been explained as being driven by chemical mechanisms, such as intricate chemical signalling among cells or genetic regulation. Now, however, researchers at the Living Matter Physics Laboratory of the Department of Physics have discovered what they call ‘self-enhanced mobility’: a simple physical mechanism that allows living matter to create ordered spatial structures spanning vast scales, purely through physical (rather than chemical) interactions.
A novel physical mechanism
The breakthrough came when two CUHK biophysicists—Dr. Haoran Xu, a postdoctoral fellow at Department of Physics, and his mentor Prof. Yilin Wu, who leads the laboratory—began to investigate patterns of turbulence in dense, active fluids composed of living bacteria. Turbulence is often seen in nature (for example, in whirlpools or whirlwinds), and is usually random, disordered and transient. But the duo discovered that living fluids consisting of self-propelling bacteria spontaneously produce a regular vortex pattern across multiple scales.
Living fluids consisting of bacteria produce a regular vortex pattern in turbulence with multiscale order (image shows an artistic illustration).
The vortices each consisted of several tens of thousands of micron-sized self-propelling bacteria. The vortices were arranged in space at a centimetre scale with apparent hexagonal order, while individual cells in the vortices moved in coordinated directions. By tracking the behaviour of individual cells and running numerical simulations, the researchers concluded that the phenomenon arises from the fact that the speed of individual cells increases with the order of local cellular movement—that is, from ‘self-enhanced mobility’.
A vast array of possible applications
The discovery of self-enhanced mobility represents a pioneering advance in the field of ‘active matter science’, a fast-growing, interdisciplinary field that studies systems consisting of units where energy is spent locally to generate mechanical work. Active matter includes all living organisms from cells to animals, biopolymers driven by molecular motors, and synthetic, self-propelled materials. Studying active matter to understand how ordered structures are produced via interaction between individual units could drive significant medical and technological innovation.
Prof. Wu said, ‘Compared with chemical or genetic regulation, this physical mechanism is a much simpler way to explain the formation of biological structures. The mechanism may help to understand ordered flow patterns in cell cytoplasm and large-scale motion patterns of cells in developing embryos of animals.’ Further along the line, the researchers expect that the findings may be applicable to tissue engineering in regenerative medicine and for controlled pattern formation in micro or nanorobotics.
Read more: