Oscillating gels could find many uses (w/ Video)

March 14, 2011 By David L. Chandler, Massachusetts Institute of Technology
Irene Chou Chen, a doctoral candidate in the lab of Krystyn J. Van Vliet. Credit: Melanie Gonick

Self-oscillating gels are materials that continuously change back and forth between different states — such as color or size — without provocation from external stimuli. These changes are caused by the Belousov-Zhabotinsky chemical reaction, which was discovered during the 1950s. Without stirring or other outside influence, wave patterns from this chemical reaction can develop within the material or cause the entire gel itself to pulsate.

Irene Chou Chen, a doctoral candidate in the lab of Krystyn J. Van Vliet, the Paul M. Cook Career Development Associate Professor of Science and Engineering, has been studying exactly how adjusting the size and shape of these gels can affect their behavior.

By integrating experiments with computer simulations conducted by collaborators Olga Kuksenok, Victor Yashin and Anna C. Balazs at the University of Pittsburgh, the MIT researchers have shown that pattern formation within the material can be controlled by changing the gel's size or shape. When the reaction is restricted to a sub-millimeter-sized gel, the material exhibits chemical oscillations that cause it to mechanically swell and shrink. Lasting for several hours, these self-sustained oscillations exemplify chemomechanical coupling — where cause mechanical changes. The work will be published in the March issue of the journal Soft Matter as part of a special focus on “active soft matter.”

Video: Melanie Gonick; additional footage: Irene Chen

The self-sustained pulsations could enable unique applications for this material, the researchers say, such as using it as an environmental sensor or as an actuator that could react to specific conditions. The simulations developed by the University of Pittsburgh group could also help to make such applications easier to implement.

Explore further: Mechanical stress leads to self-sensing in solid polymers (w/Video)

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not rated yet Mar 14, 2011
I wrote the very first simulation for this reaction (assumed points in a line) back between 1976-1977 (published JACS 1978). Accounting for diffusion, and the stiffness of the equations consumed months of computing resources.

Still, it is a straight extrapolation of that work to this. I am surprised that this wasn't done 20 years ago. At least the simulation portion anyway.
not rated yet Mar 15, 2011
Would like to see this in nematic liquid crystals for the sake of nucleating polymer ions in localized optical charge conversion for better photovoltaics.
not rated yet Mar 15, 2011
I'm new to all this but how long do these reactions last, as in the changing of colors as illustrated in the video with the grey and red? Also are these chemicals toxic?
not rated yet Mar 15, 2011
No the chemicals are not very toxic. The ingredients are malonic acid, bromine, and cerium (or some other transition metal).

The reactions last several hours. When I was doing my studies, we saw a cycles time of about 48 seconds, but I am sure that different concentrations can be used to vary the cycle time somewhat.
5 / 5 (1) Mar 15, 2011
I wrote a game a couple decades ago based on growth heuristics that animated exactly like the spiral patterns at 00:25 *Exactly* Far Out!

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