title: Wave patterns driven by chemomechanical instabilities in responsive gels.
abstract: The first experimental evidence of a chemomechanical mechanism leading to morphogenetic instabilities is demonstrated experimentally. The system consists of a pH-responsive gel that swells at high pH and shrinks at low pH, and a bistable reaction system exhibiting an acid steady state (pH approximately 2) and an alkaline steady state (pH approximately 10). Within the gel, the steady state selection depends on the gel size. We show that in a constant and uniform nonequilibrium chemical environment, the responsive gel undergoes large amplitude dynamical deformations under the form of travelling contraction waves and complex spatio-temporal volume oscillations. These deformations are coupled to concentration patterns of protons. We present different sequences of dynamical behaviors observed under various controlled chemical conditions. A simple heuristic model is proposed to account for the observations. These experiments open a new route for pattern formation driven by chemical energy, in soft matter systems.
authors.affiliation: Centre de Recherches Paul Pascal (CNRS), Av. Schweitzer, F-33600 Pessac, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Labrot
authors.forename: Patrick
authors.initials: P
authors.lastname: De Kepper
authors.forename: Jacques
authors.initials: J
authors.lastname: Boissonade
authors.forename: István
authors.initials: I
authors.lastname: Szalai
authors.forename: Fabienne
authors.initials: F
authors.lastname: Gauffre
mesh_terms: D004566:Electrodes; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000138:chemical synthesis / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D009991:Oscillometry / Q000379:methods; D010316:Particle Size; D010507:Periodicity; D013314:Stress, Mechanical
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate