Chemical brothers

2019-03-07 08:11:14

By Duncan Graham-Rowe FORGET a sophisticated brain. To find its way around, all a robot needs is a headful of chemical goo—or so, at any rate, claims an innovative team of specialists in artificial life. The idea that a liquid or gel can produce “intelligent” behaviour without any form of number crunching is not as odd as it might sound, says team member Andrew Adamatzky, a biophysicist at the University of the West of England in Bristol. It all depends upon the computational and problem-solving properties of a strange class of chemical reactions. One example is the Belousov-Zhabotinsky (BZ) reaction, in which malonic acid reacts reversibly with bromate to produce carbon dioxide. Molecules reacting in one part of the mixture trigger reactions in neighbouring areas, causing waves of reaction to pass through the mixture. These waves show up as changes in colour. The waves of the BZ reaction can also interact with each other and with features in the environment. And in 1995, a team from West Virginia University showed that the waves automatically find the quickest way through a maze ( New Scientist, 18 February 1995, p 18). Solving a maze is a formidable task, which otherwise involves examining all possible routes and working out which is the shortest. Since that discovery, mathematicians have been trying to find out if the BZ reaction can help solve other vexing problems. One of the pioneers of this field is Nicholas Rambidi of Moscow State University, who has already demonstrated the computational and problem-solving properties of BZ reactions, such as following objects and path finding. Rambidi has now teamed up with Adamatzky and his Bristol colleagues to apply the BZ reaction to controlling a robot. At the European Conference on Artificial Life in Lausanne, Switzerland, last week, the researchers announced that they have already used a simulation of the reaction to make a robot steer towards a light source. “In no way is the chemical processor programmed to produce these results,” says Owen Holland, the team’s robotics expert. “It just does it anyway because of what it is.” The BZ reaction can be triggered by light, explains Adamatzky. This means that its waves will form characteristic patterns depending on the direction of the light source. Adamatzky and his colleagues created a simulation in which the chemical solution was represented by a two-dimensional array of pixels. They took information from light sensors mounted on a real robot and “shone” these signals onto appropriate sides of the array. As waves of reaction moved through the array, information from each pixel was fed back to the robot’s motors so that it was able to follow the light source. The hard part, says Holland, who now works for the CyberLife Research Institute in Cambridge, is linking the reaction to the system that controls the motors. And while the researchers cracked that problem for their simple simulated array, using a real container of chemicals will be more tricky. Adamatzky believes that although his gooware is unlikely to out-perform computational processors,