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Chemical computers are becoming ever more of a reality - this is being proven by scientists from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw. It turns out that after an appropriate teaching procedure even a relatively simple chemical system can perform non-trivial operations. In their most recent computer simulations researchers have shown that correctly programmed chemical matrices of oscillating droplets can recognize the shape of a sphere with great accuracy.
Modern computers use electronic signals for their calculations, that is, physical phenomena related to the movement of electric charges. Information can, however, be processed in many ways. For some time now efforts have been underway worldwide to use chemical signals for this purpose. For the time being, however, the resulting chemical systems perform only the simplest logic operations. Meanwhile, researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw have demonstrated that even uncomplicated and easy-to-produce collections of droplets, in which oscillating chemical reactions proceed, can process information in a useful way, e.g. recognizing the shape of a specified three-dimensional object with great accuracy or correctly classifying cancer cells into benign or malignant.
"A lot of work being currently carried out in laboratories focuses on building chemical equivalents of standard logic gates. We took a different approach to the problem," says Dr. Konrad Gizynski (IPC PAS) and explains: "We investigate systems of a dozen-or-so to a few dozen drops in which chemical signals propagate, and treat each one as a whole, as a kind of neuronal network. It turns out that such networks, even very simple ones, after a short teaching procedure manage well with fairly sophisticated problems. For instance, our newest system has ability to recognize the shape of a sphere in a set of x, y, z spatial coordinates".
The systems being studied at the IPC PAS work thanks to the Belousov-Zhabotinsky reaction proceeding in individual drops. This reaction is oscillatory: after the completion of one oscillation cycle the reagents necessary to begin the next cycle are regenerated in the solution. A droplet is a batch reactor. Before reagents are depleted a droplet has usually performed from a few dozen to a few hundred oscillations. The time evolution of a droplet is easy to observe, since its catalyst, ferroin, changes color during the cycle. In a thin layer of solution the effect is spectacular: colorful strips - chemical fronts - traveling in all directions appear in the liquid. Fronts can also be seen in the droplets, but in practice the phase of the cycle is indicated just by the color of the droplet: when the cycle begins, the droplet rapidly turns blue (excites), after which it gradually returns to its initial state, which is red.
"Our systems basically work by mutual communication between droplets: when the droplets are in contact, the chemical excitation can be transmitted from droplet to droplet. In other words, one droplet can trigger the reaction in the next! It is also important that an excited droplet cannot be immediately excited once again. Speaking somewhat colloquially, before the next excitation it has to 'have a rest', in order to return to its original state," explains Dr. Gizynski.
Via Mariaschnee
