Abstract
We investigate the Belousov-Zhabotinzky (BZ) reaction as a substrate for computation. Expanding on previous research we present a new technique that utilizes two modes of the BZ reaction, excitation and oscillation, and selective diffusive coupling. We show in simulation that this technique can be used to invert input signals, providing the logical operator, NOT. Our system can readily compute NOR, which when connected in multiples is sufficient for simulating any other logical operator. Furthermore, progress to experimentally implement these operators and to wire them into circuits using soft lithography and replica molding is presented. To synthesize living systems the field of artificial life has explored numerous substrates, physical and virtual. Chemical substrates have been gaining in popularity with recent advances in chemical computation (Adamatzky, 2009; Gorecki, 2009) and cognition (Dale and Husbands, 2010). In Braitenberg’s series of vehicles of increasing cognitive complexity a key turning point is the introduction of inhibitory threshold devices, allowing for the use of numbers, logic, and basic memory (Braitenberg, 1986). Though to an extent the latter two properties have been introduced in our choice substrate, the Belousov-Zhabotinzky (BZ) reaction, true inhibition in the BZ has not been achieved. Here we applied the novel concept of inhibitory coupling (Toiya et al. 2008) to design signal inverting logic gates. Using BZ substrate, various logic gates have been implemented experimentally or by computer simulation. Gorecki has simulated the gates AND and OR, as well as the MAJORITY function. Adamatzky showed XOR and AND in a related experimental substrate. Collision dynamics of BZ waves have also been exploited to annihilate signals (de Lacy Costello, 2009)