Aumaitre Elodie, Knoche Sebastian, Cicuta Pietro, Vella Dominic
Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK.
Eur Phys J E Soft Matter. 2013 Mar;36(3):22. doi: 10.1140/epje/i2013-13022-3. Epub 2013 Mar 18.
The protein hydrophobin HFBII self-assembles into very elastic films at the surface of water; these films wrinkle readily upon compression. We demonstrate and study this wrinkling instability in the context of non-planar interfaces by forming HFBII layers at the surface of bubbles whose interfaces are then compressed by deflation of the bubble. By varying the initial concentration of the hydrophobin solutions, we are able to show that buckling occurs at a critical packing fraction of protein molecules on the surface. Independent experiments show that at this packing fraction the interface has a finite positive surface tension, and not zero surface tension as is usually assumed at buckling. We attribute this non-zero wrinkling tension to the finite elasticity of these interfaces. We develop a simple geometrical model for the evolution of the wrinkle length with further deflation and show that wrinkles grow rapidly near the needle (used for deflation) towards the mid-plane of the bubble. This geometrical model yields predictions for the length of wrinkles in good agreement with experiments independently of the rheological properties of the adsorbed layer.
疏水蛋白HFBII在水表面自组装成具有很高弹性的薄膜；这些薄膜在压缩时很容易起皱。我们通过在气泡表面形成HFBII层，然后通过气泡放气来压缩其界面，在非平面界面的背景下演示并研究这种起皱不稳定性。通过改变疏水蛋白溶液的初始浓度，我们能够表明，在表面蛋白质分子的临界堆积分数下会发生屈曲。独立实验表明，在这个堆积分数下，界面具有有限的正表面张力，而不是像通常在屈曲时所假设的零表面张力。我们将这种非零起皱张力归因于这些界面的有限弹性。我们开发了一个简单几何模型，用于描述随着进一步放气皱纹长度的演变，并表明皱纹在靠近（用于放气的）针处朝着气泡的中平面快速生长。这个几何模型对皱纹长度的预测与实验结果非常吻合，且与吸附层的流变特性无关。
