Three-dimensional chemical waves in the Belousov–Zhabotinskii reaction

Abstract

A simply-connected region of the Belousov–Zhabotinskii (B–Z) reaction medium may produce a variety of three-dimensional wave forms of unusual geometry. The reaction–diffusion hypothesis even in its linear formulation supports iso-concentration surfaces which include helical surfaces and toroidal scroll waves with twists¹. A variety of other wave forms has been proposed by Winfree and Strogatz². Experimental difficulties associated with observations in three dimensions have precluded confirmation of these waves in situ. We now present direct experimental evidence of evolving three-dimensional chemical waves. Our design is easy to implement, lends itself to time-delay photography and is essentially free of difficulties pointed out earlier³. The dominant wave forms are toroidal scrolls^{1, 3–5}; other wave forms observed include the sphere-like structure predicted recently².