The well-studied Belousov-Zhabotinsky (BZ) reaction is a complicated process in which an ion's oxidation state oscillates, changing colors as it goes. The reaction produces striking, evolving wave patterns and is often used to study wave behavior.

Now, West Virginia University chemistry professor Kenneth Showalter, postdocs Tatsunari Sakurai and Eugene Mihaliuk, and graduate student Florin Chirila show they can control the waves in a BZ reaction, creating any pattern they wish (Science, published online May 2, http://sciencemag.org/cgi/content/abstract/1071265v1).

The group members have developed a feedback system to steer the direction of the waves by using light to change what's called the local excitability--the ability of the system to respond to perturbations--around the wave. They can design trajectories such as the hypotrochoid paths shown left, top and bottom, in multiple exposures taken every 40 seconds. For comparison, theoretical calculations are shown on the right.

But what is such control good for? "That is always the $64,000 question," Showalter tells C&EN. "I think we have learned a great deal about how waves interact with a dynamically varying medium." Biology is rife with such wave phenomena, for one example, and controlling the processes will go a long way toward helping scientists understand them.

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