Department of Materials, ETH Zürich, 8093, Zürich, Switzerland.
Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA.
Nat Commun. 2017 Sep 15;8(1):555. doi: 10.1038/s41467-017-00636-y.
Surface stress, also known as surface tension, is a fundamental material property of any interface. However, measurements of solid surface stress in traditional engineering materials, such as metals and oxides, have proven to be very challenging. Consequently, our understanding relies heavily on untested theories, especially regarding the strain dependence of this property. Here, we take advantage of the high compliance and large elastic deformability of a soft polymer gel to directly measure solid surface stress as a function of strain. As anticipated by theoretical work for metals, we find that the surface stress depends on the strain via a surface modulus. Remarkably, the surface modulus of our soft gels is many times larger than the zero-strain surface tension. This suggests that surface stresses can play a dominant role in solid mechanics at larger length scales than previously anticipated.Solid surface stress is a fundamental property of solid interfaces. Here authors measure the solid surface stress of a gel, and show its dependence on surface strain through a surface modulus.
表面应力，又称表面张力，是任何界面的基本材料特性。然而，在传统工程材料（如金属和氧化物）中测量固体表面应力一直非常具有挑战性。因此，我们的理解严重依赖未经测试的理论，尤其是关于该特性对应变的依赖性。在这里，我们利用软聚合物凝胶的高顺应性和大弹性变形能力，直接测量应变下的固体表面应力。正如针对金属的理论工作所预期的那样，我们发现表面应力通过表面模量与应变相关。值得注意的是，我们的软凝胶的表面模量比零应力量纲的表面张力大几个数量级。这表明表面应力在比之前预期的更大的长度尺度上可以在固体力学中起主导作用。固体表面应力是固体界面的基本特性。在这里，作者测量了凝胶的固体表面应力，并通过表面模量显示了其对表面应变的依赖性。
