Oscillating chemical waves process images.

Oscillating chemical waves process images

Computerized image processing typically involves assigning numerical values to each of an image's variously bright or colored points and then manipulating those values to enhance the contrast, change or add colors, fill in gaps, or perform other graphical transformations.

Can a thin liquid layer of chemicals in a petri dish behave like an image processing computer? Maybe, according to a report in the Jan. 19 NATURE. Most computers sequentially process each point of an image. But some chemical systems such as the Belousov-Zhabotinskii (BZ) reaction, which slowly oscillates between blue and orange states, work on every point at once. This chemical layer seems to temporarily store images, enhance contours and smooth "partially degraded pictures."

The BZ reaction is actually a series of reactions involving bromine-containing chemicals, acidic organic molecules such as malonic acid, and a catalyst. One set of reactions (orange) predominates at low bromide ion concentrations; another (blue) at higher ion levels. The system oscillates between the two sets of reactions because the first reaction set paves the way for the second by consuming bromide ions. But the products of the latter reactions promote the catalytically driven liberation of bromide ions. The return of the free ions resets the stage for the first reaction set and a new cycle.

The researchers made alight-sensitive version of the BZ reaction by using a ruthenium metal catalyst, whose bromide-liberating behavior changes when it absorbs light. Exposing the chemical layer in the petri dish with a half-tone image initiates a pattern of oscillating reaction zones that together appear as alternating positive and negative exposures of the image. At first, the exposed zones remain blue because light both increases local bromide concentrations and delays the onset of the orange-producing reaction set. Unexposed zones turn orange sooner. The two types of zones, now oscillating out of phase with each other, periodically exchange colors in the now nonhomogeneous layer.

The researchers -- Lothar Kuhnert of the Max Planck Institute for Nutritional Physiology in Dortmund, West Germany, and K.I. Agladze and V.I. Krinsky of the Institute of Biophysics in Pushchino, USSR--suggest their chemical system may be more than a laboratory curiosity. "My aim was to construct a light-sensitive system, but I was surprised by how it works as an image processor," Kuhnert told SCIENCE NEWS. Still, the layer can "store" images only temporarily, so its fleeting information must be captured on film, he concedes.