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Echoes discovered in chemical reactions

Echoes exist in many forms: reflections of sound in acoustics, signal reflections in telecommunication frequencies, even Amazon’s new “smart” speaker. 

Echo phenomena now even span to chemistry. A team of West Virginia University researchers discovered echo behavior in chemical reactions in December following a three-year study. A system of coupled chemical oscillators, totaling more than 1,000 tiny chemical reactions, demonstrated the echo phenomenon. 

Kenneth Showalter
Kenneth Showalter

The findings are featured in the scientific journal Physical Review X, published by the American Physical Society. 

“What’s new about this work is that ordinary chemical oscillators can exhibit echo behavior. We wanted to find a way to show that this phenomenon could actually happen in a real system,” said Kenneth Showalter, professor in the C. Eugene Bennett Department of Chemistry. “After working hard and long with several false starts, we finally made it happen.”

Echoes occur after a delay following the immediate responses to two successful stimuli. In the case of the chemical oscillators, the echo appeared as the alignment of oscillator phases rather than sound. The oscillator phases were measured by the transmitted light intensity of each oscillator.  

Mark Tinsley
Mark Tinsley

The research team, which includes Showalter, WVU teaching assistant professor Mark Tinsley, WVU alumnus Tianran Chen and University of Maryland theoretical chemist Edward Ott, monitored more than 1,000 tiny reactor beads, each with their own oscillation frequency.  

After the reactor beads have cycled many times through their oscillators following the stimuli, they aligned independently without any additional stimuli, demonstrating the echo. The echo occurs because the oscillators retain memory of the stimuli.

The discovery of the chemical echo has the potential to lead to a variety of multidisciplinary applications because chemical oscillators behave similarly to other oscillators, such as biological oscillators. Oscillatory cells are common—bacteria, yeast, neurons and heart cells, to name a few.  

“It should be possible to observe echo behavior in these biological systems since it is seen in chemical oscillators,” Showalter said. 

Photo credit: Andy Langager

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