Chandler Thomas G J, Ferria Jordan, Shorthose Oliver, Allain Jean-Marc, Maiolino Perla, Boudaoud Arezki, Vella Dominic
Mathematical Institute, University of Oxford, Woodstock Rd, Oxford OX2 6GG, UK.
Department of Mathematics, University of Wisconsin-Madison, Madison, WI 53706, USA.
J R Soc Interface. 2025 Feb;22(223):20240653. doi: 10.1098/rsif.2024.0653. Epub 2025 Feb 12.
Everyday experience shows that cellular sheets are stiffened by the presence of a pressurized gas: from bicycle inner tubes to bubble wrap, the presence of an internal pressure increases the stiffness of otherwise floppy structures. The same is true of plants, with turgor pressure (due to the presence of water) taking the place of gas pressure; indeed, in the absence of water, many plants wilt. However, the mechanical basis of this stiffening is somewhat opaque: simple attempts to rationalize it suggest that the stiffness should be independent of the pressure, at odds with everyday experience. Here, we study the mechanics of sheets that are a single-cell thick and show how a pressure-dependent bending stiffness may arise. Our model rationalizes observations of turgor-driven shrinkage in plant cells and also suggests that turgor is unlikely to provide significant structural support in many monolayer leaves, such as those found in mosses. However, for such systems, turgor does provide a way to control leaf shape, in accordance with observations of curling upon drying of moss leaves. Guided by our results, we also present a biomimetic actuator that uncurls upon pressurization.
日常经验表明，细胞片层会因有压力的气体的存在而变硬：从自行车内胎到气泡膜，内部压力的存在会增加原本柔软结构的硬度。植物也是如此，膨压（由于水的存在）取代了气压；事实上，在缺水的情况下，许多植物会枯萎。然而，这种变硬的力学基础有些晦涩难懂：简单的合理解释表明，硬度应该与压力无关，这与日常经验相悖。在这里，我们研究了单细胞厚度的片层的力学原理，并展示了与压力相关的弯曲刚度是如何产生的。我们的模型解释了植物细胞中膨压驱动收缩的观察结果，还表明在许多单层叶片（如苔藓中的叶片）中，膨压不太可能提供显著的结构支撑。然而，对于这样的系统，膨压确实提供了一种控制叶片形状的方式，这与苔藓叶片干燥时卷曲的观察结果一致。受我们结果的启发，我们还展示了一种加压时会展开的仿生致动器。
