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J Boissonade

Publications and source records attributed to J Boissonade.

10 recordsLinked to original sources
PubMed2006

Spatial bistability: a source of complex dynamics. From spatiotemporal reaction-diffusion patterns to chemomechanical structures.

We show experimentally and theoretically that reaction systems characterized by a slow induction period followed by a fast evolution to equilibrium can readily generate "spatial bistability" when operated in thin gel reactors diffusively fed from one side. This phenomenon which corresponds to the coexistence of two different stable steady states, not breaking the symmetry of the boundary conditions, can be at the origin of diverse reaction-diffusion instabilities. Using different chemical reactions, we show how stationary pulses, labyrinthine patterns or spatiotemporal oscillations can be generated. Beyond simple reaction-diffusion instabilities, we also demonstrate that the cross coupling of spatial bistability with the size responsiveness of a chemosensitive gel can give rise to autonomous spatiotemporal shape patterns, referred to as chemomechanical structures.

Catalysis↗
PubMed2005

Spatial bistability in a pH autocatalytic system: from long to short range activation.

The acid-auto-activated chlorite-tetrathionate reaction is studied in a one-side-fed spatial reactor. It was previously shown that in these conditions the unstirred reaction-diffusion system can generate oscillatory and excitable states even though under well-stirred nonequilibrium conditions only steady-state bistability is observed. Numerical simulations suggest that these temporal reaction-diffusion instabilities result from long-range activation by rapidly diffusing protons. We study here experimentally and numerically the effect of introducing into this reaction-diffusion system macromolecular carboxylate species that reduce the effective diffusivity of protons. Consistent with the original assumption, the introduction of such slow mobility proton-binding species quenches both oscillatory and excitability dynamics. Within the bistability domain the direction of the propagation of an interface between the two steady states depends on control parameter value. We elaborate on the fact that beyond a low critical concentration of macromolecular carboxylate species, the stability limit of the "thermodynamic" branch of spatial steady state does not depend on this concentration. Despite the relative simplicity of the kinetic model used in the numerical simulations, the results are in quasi-quantitative agreement with the experimental observations.

Journal Article↗
PubMed2005

Self-oscillations in chemoresponsive gels: a theoretical approach.

Some gels can swell or shrink in function of the concentration of the solutes contained in the solvent. We develop and discuss an algorithm based on Stefan-Maxwell equations to study the dynamics of a sphere of chemoresponsive gel immersed in a medium kept far from equilibrium. We show that the coupling of the reaction with these volume changes creates some feedback that can lead to chemomechanical instabilities. As a result, a reaction that is not oscillatory in homogeneous conditions or in a nonresponsive gel can induce self-oscillations of volume and concentrations in a responsive gel. We also show that chemical oscillations related to long range activation can be strongly modified in such gels, even when the changes of volume are small.

Journal Article↗
PubMed2004

Spatial bistability and excitability in the chlorite-tetrathionate reaction in cylindrical and conical geometries.

Spatial bistability and excitability in the chlorite-tetrathionate reaction, performed in gels fed by diffusion from one boundary, have been extensively studied, both experimentally and numerically, in a flat annular striplike geometry. We first complement these numerical results. Afterwards, we extend the calculations to the cylindrical and conical geometries. In the cylinder, we compute the limits of bistability and of excitability which are important for experiments in chemomechanics but cannot be directly measured. The results of the simulations in the conical geometry agree with previous experiments on the corresponding setup. We show that the characteristics of the traveling waves which spontaneously arise in the latter geometry provide a simple and direct experimental access to these limits.

Journal Article↗
PubMed2003

Simple chemomechanical process for self-generation of rhythms and forms.

We show that cross-coupling between the geometrical changes and the chemical reaction-diffusion regimes within a piece of gel embedded in a stationary reactive medium kept far from equilibrium can destabilize the trivial steady state and lead to spatiotemporal dissipative structures. The involved physical processes are the spatial bistability and the swelling properties of the gel. As an illustration of this morphogenetic process, we show that a sphere of gel immersed within such a medium with autocatalytic properties can exhibit periodic radius pulsations, the amplitude of which are controlled by chemistry.

Biomimetic Materials↗
PubMed2002

Dynamical effects induced by long range activation in a nonequilibrium reaction-diffusion system.

We show both experimentally and numerically that the time scales separation introduced by long range activation can induce oscillations and excitability in nonequilibrium reaction-diffusion systems that would otherwise only exhibit bistability. Namely, we show that in the chlorite-tetrathionate reaction, where the autocatalytic species H+ diffuses faster than the substrates, the spatial bistability domain in the nonequilibrium phase diagram is extended with oscillatory and excitability domains. A simple model and a more realistic model qualitatively account for the observed dynamical behavior. The latter model provides quantitative agreement with the experiments.

Journal Article↗
PubMed2001

Spatial bistability and waves in a reaction with acid autocatalysis.

The phenomenon of spatial bistability has recently been proposed for a comprehensive understanding of a number of chemical patterns observed in open spatial reactors consisting of thin films of gel diffusively fed from one side. We study experimentally and numerically this phenomenon in the tetrathionate-chlorite reaction characterized by an acid superautocatalysis. We focus on the similarities and differences with previous studies on the chlorine dioxide-iodide reaction. In addition, we show that this reaction, which is only bistable in a continuous stirred tank reactor, can exhibit oscillatory and traveling waves when diffusion comes into play. Our computations suggest that the nonstationary behaviour originates from differential diffusive transport.

Journal Article↗
PubMed1996

Chemical morphogenesis: turing patterns in an experimental chemical system.

Patterns resulting from the sole interplay between reaction and diffusion are probably involved in certain stages of morphogenesis in biological systems, as initially proposed by Alan Turing. Self-organization phenomena of this type can only develop in nonlinear systems (i.e. involving positive and negative feedback loops) maintained far from equilibrium. We present Turing patterns experimentally observed in a chemical system. An oscillating chemical reaction, the CIMA reaction, is operated in an open spatial reactor designed in order to obtain a pure reaction-diffusion system. The two types of Turing patterns observed, hexagonal arrays of spots and parallel stripes, are characterized by an intrinsic wavelength. We identify the origin of the necessary diffusivity between activator and inhibitor. We also describe a pattern growth mechanism by spot splitting that recalls cell division.

Animals↗