A team from the University of Amsterdam (UvA) has demonstrated that activity — the inherent motion of living or active particles — can suppress a classic phase transition essential for self-organization in soft matter. In passive systems like rods or liquid crystals, packing elongated objects together forces them to align. But replace those inert rods with active entities such as worms or gut bacteria, and that order breaks down.
The finding challenges long-held assumptions about how complex biological materials organize. The nematic phase transition, where string-like components spontaneously align, underpins everything from display technology to understanding bacterial colonies. Now, researchers have shown that when objects move on their own, they can “fundamentally alter” this process, according to the team.
Experiments and simulations revealed that active motion introduces persistent fluctuations that prevent the system from settling into a uniform aligned state. Instead of falling into a neat pattern, the active particles remain in a dynamic, disordered phase. This suggests that living matter operates under different physical rules than static materials.
The implications stretch across biology and materials science. Understanding how bacteria or cellular filaments organize could reshape models of biofilm formation or tissue behavior. Conversely, engineers designing active materials — from self-healing polymers to swarm robotics — may need to account for this disruption of order.
The UvA team cautions that the study is based on simplified models of activity. Real biological systems include additional factors like chemical signaling or shape changes, which could either amplify or counteract the effect. More research is needed to test the findings in living organisms.