Professor explains her findings on active materials
Swimming en masse, schools of fish seem to defy the laws of nature — each fish appears to know its place, never becoming disoriented or breaking formation. According to Prof. Aparna Baskaran (PHYS), the science behind this boils down to one thing: active materials.
Active materials, Baskaran explained in a lecture last Tuesday, are “made out of engines, which consume fuel to do work.” In other words, every individual fish applies its own force to its surrounding environment to propel itself, with the school being merely a result of them all moving in the same place at the same time.
In her introduction, Baskaran explained what an active material is and revealed some of its potential applications, including in the understanding of the “physical scaffold” of biological systems. She also noted that active materials may allow scientists to design adaptive, self-healing materials in the future by utilizing active particles’ natural tendency to stay closely together.
Baskaran’s first example supporting her theory explained a system she referred to as an “active colloid,” or a system of simulated particles which move in one direction at all times. In this simulated system, she noted, the particles had a tendency to run into each other and form a clump because, instead of bouncing off each other like normal objects, the particles block each other from moving forward.
This, Baskaran said, is a potential reason why fish stay in a school: not because they collide, but because the force of the fish propelling themselves has a tendency to keep them close to one another.
The second example Baskaran gave concerned a different system, which she called a “nematic fluid.” These are particles which, instead of exerting force in one direction at all times, exert force in two opposite directions.
The simulation her lab conducted consisted of tiny rods with attractive force between them, and while the results were fairly consistent with expectations in a theoretical vacuum with no external forces, the results became less predictable once the limitations of the real world were added in. “There are more things to understand than there are understood, so this is very much a work in progress,” Baskaran admitted.
Baskaran has overseen the entire process of active material research at the University, but as she stressed, “My students and post-docs did the work, and I like to think we did it together.”
“The most exciting part of my research is the development of synthetic active materials. Biology is messy and hard to predict, so being able to create our own materials makes them easier to study,” Baskaran said in a follow up interview with the Justice. “This is the cutting edge of materials research, and Brandeis is one of the leading centers in that field. This is something we as a community can be proud of.”
Baskaran’s talk on her findings was the first of the 2016 Physics Colloquium season, a series of lectures during which the Physics department comes together to discuss new findings.