Self-oscillating gels continuously change back and forth between different states — such as color or size — without external stimuli. These changes are caused by the Belousov-Zhabotinsky (BZ) reaction, which can cause wave patterns in the material or cause the entire gel to pulsate.
Krystyn Van Vliet and colleagues, Massachusetts Institute of Technology, USA, have studied N-isopropylacrylamide gels containing covalently bound BZ catalyst and polyacrylamide-silica gel composites containing physically associated BZ catalyst, both experimentally and with computer simulations. They show that the pattern of the oscillations within BZ gels can be altered by changing the shape and size of the gels.
The gels were seen to shrink and swell when the reaction was restricted to a sub-millimeter-sized gel. The oscillations were self-sustaining over a period of several hours. This discovery moves BZ gels from being a curiousity to having practical applications such as environmental sensors or actuators that react to specific conditions.
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