Information Technology Reference
In-Depth Information
In this case, the projected light image is converted into a distribution of chemical
components of the medium. Two main factors determine the adequacy of the
distribution of concentrations of medium components with respect to the original
light pattern.
First of all, it is the minimum value and, most importantly, the uniformity of the
light background of the optical device used to input the original image. Any
heterogeneity may cause a dynamic process in the medium not associated with
the input data.
Secondly, it is the constancy of the thickness of the medium, which may be
disrupted due to a manufacturing error of the reactor, in which the process takes
place, its inaccurate leveling, etc. This results in additional gradients of concentra-
tion of the chemical components of the medium, which also leads to random
dynamic processes interfering with the investigated dynamics.
A planar polymer layer of a given thickness that does not interact chemically
with the components of the medium is a spatial matrix of the polymer substance
containing 80-90 % water. If the water is replaced by the reagent of the reaction-
diffusion system, the thickness of the reagent layer will be maintained by the
polymer matrix. As a result, the reagent layer will be affected neither by the errors
of the reactor and of leveling nor by random mechanical effects (shock, vibration,
etc.).
Polymeric materials allow for creating spatially inhomogeneous media with a
given structure
.
Let us consider just two examples of the formation of such systems.
The problem of finding the shortest path in a maze was considered above. The
characteristic property of the formation of the medium used for this purpose was
immobilization of the catalyst of the chemical reaction in a thin silica gel layer. This
allowed to fix the distribution of the reaction components, corresponding to the
labyrinth, and to organize the wave process propagating along it.
A somewhat more complex design of the medium was used by Steinbock and
colleagues who modeled logic devices, switchable by a wave process in a reaction-
diffusion medium. The picture of the device was applied by a printer to the surface
of a thin ion exchange membrane catalyst using the solution of the reaction's
catalyst instead of the printer ink. The membrane itself was placed on a layer of
agar gel, which contained the remaining components of the chemical reagent.
Polymer matrices can control the processes in the environment
.
N. Kazanskaya with coworkers developed two systems in which the polymer
matrix plays an active role.
The first of these is a combination of two polymeric membranes. One of them
contained a photosensitive component—spiropyran. Additionally, the ionophore
nonactin was injected into the membrane to couple the membrane photoresponse
with urea hydrolysis occurring on another membrane and catalyzed by urease.
The second system was a two-level spatially combined one. It consisted of a
polymer matrix, saturated with urease, which hydrolyzed urea. Enzyme activity
was a function of temperature near the point of reversible collapse of the gel of the
matrix.
