Microscopic Particles Dance to the Tune of Electrochemical ReactionsA recent University of Maryland study revealed a coordinated dance of microscopic particles—breaking up and clustering back together in just seconds—after receiving electrical and chemical stimuli. This work represents a new class of materials that mimic the behaviors of living organisms, known as “active matter.” Like the skin of a chameleon or octopus, which respond to external stimuli by changing colors, “active matter” encompasses a group of materials that are programmed to display dynamic and autonomous behavior, such as motility, assembly, or swarming. Today, a study by Associate Professor Taylor Woehl revealed a new mechanism to activate these properties in a matter of seconds, published in the journal Nature Communications. Researchers in the Department of Chemical and Biomolecular Engineering discovered a method that consists of shocking microscopic particles in liquid with an electrical current, which entices the particles to assemble into crystals that disassemble and reassemble in a repeating cycle. While previous researchers demonstrated the ability to instill these behaviors in particles, they required actively changing the stimulus over time similar to programming a robot. Instead, Woehl’s team discovered a method that promotes this cycle to occur independently during seconds using a constant stimulus. Put simply, the microscopic particles dance to the tune of electrically stimulated chemical reactions.
“In that way, it’s more similar to a biological system, but what’s really happening in the background are chemical reactions telling these particles what to do,” said Woehl. Biological cells utilize chemical signals to replicate, move, and perform functions autonomously and within time scales of minutes. Previous attempts at using chemical signals to entice “active matter” to exhibit similar dynamic behavior have resulted in systems with very slow response times of hours to days. Likewise, prior methods using electric voltage to coordinate clustering of microscopic particles have lacked control over how long the particles cluster. Woehl’s method overcomes these prior hurdles by combining electric voltage and chemical signals to enable coordinated clustering of microscopic particles with precise control over response time. The study was a collaboration between Woehl and Associate Professor Paul Albertus’ research group, where Albertus contributed theoretical modeling to understand how the electric voltage controlled the chemical stimulus. This enabled predicting how changes in the electric stimulus would impact solution acidity and thus the response of the microscopic particles. The broader impact of this work lies in a novel method for converting particles composed of inert silicon dioxide into active matter for dynamic photonic materials like active camouflage or smart windows, which have potential defense and sustainability applications. The project was funded by a National Science Foundation’s Particulate and Multiphase Processes program, which supports fundamental research on physico-chemical phenomena that govern particulate and multiphase systems.
March 2, 2025 Prev Next |
