What are the currents in Bhilai IIT

Researchers at the Max Planck Institute for Intelligent Systems have observed a new example of pattern formation in active matter. They enclosed nanoparticles in a drop of water that were chemically active with UV light. With a high density of particles, a flow pattern was created spontaneously by breaking symmetry. And not only that: each drop communicated with neighboring drops through the exchange of chemicals that coordinated the respective internal currents - even when they were far apart.

 

Stuttgart - Communication and organized behavior are considered the quintessence of life. One of the most interesting phenomena in biological systems is, for example, understanding how cellular patterns emerge.

Knowledge about the ability of nature to actively organize itself is used by science in a variety of ways - including to develop new interactive materials. Scientists at the Laboratory for Micro, Nano and Molecular Systems at the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart have now succeeded in making drops with nanoparticles organize themselves and communicate with one another. Her research work "Interface-mediated spontaneous symmetry breaking and mutual communication between drops containing chemically active particles" was published on May 5, 2020 in the journal Nature Communications.

The MPI-IS researchers worked with scientists from the University of Seville in Spain. Together they found a simple but highly interactive form of active matter. They used powder made of titanium dioxide (TiO2), added peroxide and put the mixture in a drop of water. “A chemical reaction takes place on the particles when we irradiate them with UV light. Although the individual particles are immobile, it is very different when many of them come together. By enclosing a large number of nanoparticles in a drop, we were able to generate and observe a very dense system of active particles, ”explains Dhruv Singh, the first author of the study. Until recently, Singh was a postdoc at the MPI-IS; He is currently Assistant Professor at the Indian Institute of Technology Bhilai in India. “The droplet with the TiO2 particles was carefully placed in oil. With the lighting, we saw how currents developed spontaneously within the drop and how the particles organized themselves into a defined pattern, ”adds Singh.

Illustration: A single drop with active nanoparticles that collectively organize (left); as well as several drops that communicate and coordinate their flow patterns (right).

 

The researchers explain the phenomenon through a novel mechanism based on the one hand on the spatial encapsulation in the droplet and on the other hand on the changes in the chemical composition of the interface of the droplet that generate the currents (Marangoni effects) and on the chemical reactions of the particles be evoked. It is noteworthy that within each drop not only does self-organization take place, but each drop interacts spontaneously with neighboring drops, which all “coordinate” their flows - even if they are far apart.

"Our study illustrates how active particles - when they occur in large numbers and in high density - form macroscopically ordered systems and can communicate chemically," says Peer Fischer, head of the Micro, Nano and Molecular Systems Laboratory at the MPI-IS and professor of physics Chemistry at the University of Stuttgart. “We have implemented high-density active systems and found a model system for investigating collective phenomena. The drops can be used to achieve complex flow behavior and thus to pump liquids, ”concludes Singh.


self-organization of active matter nanoparticles Communication and organized behavior siegfried dietrich peer fischer Dhruv Singh