Leocmach Mathieu, Nespoulous Mathieu, Manneville Sébastien, Gibaud Thomas
Université de Lyon, Laboratoire de Physique, Éccole Normale Supérieure de Lyon, CNRS UMR 5672, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
Sci Adv. 2015 Oct 16;1(9):e1500608. doi: 10.1126/sciadv.1500608. eCollection 2015 Oct.
Confined thin surfaces may wrinkle as a result of the growth of excess material. Elasticity or gravity usually sets the wavelength. We explore new selection mechanisms based on hydrodynamics. First, inspired by yoghurt-making processes, we use caseins (a family of milk proteins) as pH-responsive building blocks and the acidulent glucono-δ-lactone to design a porous biogel film immersed in a confined buoyancy-matched viscous medium. Under specific boundary conditions yet without any external stimulus, the biogel film spontaneously wrinkles in cascade. Second, using a combination of titration, rheology, light microscopy, and confocal microscopy, we demonstrate that, during continuous acidification, the gel first shrinks and then swells, inducing wrinkling. Third, taking into account both Darcy flow through the gel and Poiseuille flow in the surrounding solvent, we develop a model that correctly predicts the wrinkling wavelength. Our results should be universal for acid-induced protein gels because they are based on pH-induced charge stabilization/destabilization and therefore could set a benchmark to gain fundamental insights into wrinkled biological tissues, to texture food, or to design surfaces for optical purposes.
受限的薄表面可能会因多余材料的生长而产生皱纹。弹性或重力通常决定了波长。我们探索基于流体动力学的新选择机制。首先，受酸奶制作过程的启发，我们使用酪蛋白（一类乳蛋白）作为pH响应构建块，并使用酸化剂葡萄糖酸-δ-内酯来设计一种浸入受限浮力匹配粘性介质中的多孔生物凝胶膜。在特定边界条件下且无任何外部刺激时，生物凝胶膜会自发地呈级联状起皱。其次，通过滴定、流变学、光学显微镜和共聚焦显微镜的组合，我们证明在持续酸化过程中，凝胶先收缩然后膨胀，从而引发起皱。第三，考虑到通过凝胶的达西流和周围溶剂中的泊肃叶流，我们开发了一个模型，该模型能正确预测起皱波长。我们的结果对于酸诱导的蛋白质凝胶应该是通用的，因为它们基于pH诱导的电荷稳定/不稳定，因此可以为深入了解起皱的生物组织、食品质地或设计光学用途的表面设定一个基准。
