Named a swirlonic state, the newly-discovered state of active matter is comprised of swirlons, formed by groups of active quasiparticles orbiting their common center of mass.
Active matter is a substance comprised of active particle that demonstrate the motility, that is the ability to exhibit motion and to perform mechanical work at the expense of metabolic energy.
The active particles consume energy from the environment and drive themselves far from equilibrium.
Living matter provides an uncountable amount of examples of active particles systems. Other examples refer to robotics, biomedicine, and social science.
The most prominent feature of systems of active particles is the formation of self-organized structures. Among these are intriguing milling patterns emerging in circular motion, when a group of individuals follow one another around an empty core.
Such swirling patterns have been observed for animals at different evolution stages, ranging from plant-animal worms and insects to fish.
In the new study, University of Leicester’s Professor Nikolai Brilliantov and colleagues investigated large systems of active particles.
They observed the formation of conventional gaseous, liquid, and solid phases, but also a new state of active matter — a swirlonic state.
This novel state displayed a stunning behavior whereby instead of moving with acceleration, groups of quasiparticles moved with a constant velocity, proportional to the applied force and in the same direction of the force. This conduct seemingly violates the Second Newton’s Law.
“We were completely baffled to witness how these quasiparticles swirl within active matter, behaving like individual super-particles with surprising properties including not moving with acceleration when force is applied, and coalescing upon collision to form swirlons of a larger mass,” Professor Brilliantov said.
“These patterns have previously been observed for animals at different evolution stages, ranging from plant-animal worms and insects to fish, but rather as singular structures, not as a phase which borders other phases, resembling gaseous and liquid phases of ‘normal’ matter.”
“It is always exciting to consider deepening our understanding of novel phenomena and their guiding physical principles,” added Professor Ivan Tyukin, also from the University of Leicester.
“What we know to date is so much less than what there is to know.”
“The phenomenon of the ‘swirlon’ is part of the tip of the iceberg of hidden knowledge. It leaves us with the eternal question: What else don’t we know?”
The discovery is reported in a paper published in the journal Scientific Reports.
N.V. Brilliantov et al. 2020. Swirlonic state of active matter. Sci Rep 10, 16783; doi: 10.1038/s41598-020-73824-4