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 scrolls1, 3–5; other wave forms observed include the sphere-like structure predicted recently2.