ON MULTITASKING IN PARALLEL CHEMICAL PROCESSORS: EXPERIMENTAL FINDINGS

Abstract

A parallel chemical processor is a thin-layer of a reagent mixture which reacts to changes in its concentration — data configuration — in a predictable way to form a stationary pattern corresponding to the concentration of the reagent — result configuration. A computation in the chemical processor is implemented via the spreading and interaction of diffusive or phase waves. We design chemical processors that solve a classical problem of computational geometry — computation of a Voronoi diagram. Namely, we study the possibility of designing a multitasking chemical processor that independently and simultaneously computes Voronoi diagrams of two different data planar sets. We define a two-tasking chemical processor as two distinct reactant–substrate couples within a reaction–diffusion processor that solve separate tasks but share the same physical space. A micro-volume of the physical space is an elementary processor of a massively parallel chemical processor, therefore two reaction–diffusion systems occupying the same space are considered to be a single chemical processor. We found that when a single reactant is on a gel layer containing either one or two substrates the same single Voronoi diagram corresponding to the original location of the reactant drops is constructed. However, when two reactants are on a gel containing two substrates and where there is extremely limited cross reactivity between the separate reactant-substrate couples then two Voronoi diagrams of the data planar points (two sets of drops of separate reactants) are constructed; the third "complementary" pattern is also constructed. The first Voronoi diagram constructed is identical at least in position to the one constructed where one reactant was with one substrate (with the same original configuration of reactant drops). After the formation of the first diagram is completed the diffusion fronts corresponding to unlike reactants cross and are only annihilated where they meet another reactant front composed of the same reactant. The result is the computation of two additional Voronoi diagrams pertaining to the spatial positions of the two sets of reactant drops. The outcomes of this experiment albeit in a simple chemical system are significant because the system constitutes the first class of a synthetic chemical parallel processor capable of at least two computations at the same time.