Université Montpellier 2, Laboratoire Charles Coulomb, UMR 5521, F-34095 Montpellier Cedex 5, France.
Phys Rev Lett. 2013 Aug 2;111(5):058302. doi: 10.1103/PhysRevLett.111.058302.
We report theoretical predictions and measurements of the capillary force acting on a spherical colloid smaller than the capillary length that is placed on a curved fluid interface of arbitrary shape. By coupling direct imaging and interferometry, we are able to measure the in situ colloid contact angle and to correlate its position with respect to the interface curvature. Extremely tiny capillary forces down to femtonewtons can be measured with this method. Measurements agree well with a theory relating the capillary force to the gradient of Gaussian curvature and to the mean curvature of the interface prior to colloidal deposition. Numerical calculations corroborate these results.
我们报告了对作用于放置在任意形状弯曲流体界面上的小于毛细长度的球形胶体的毛细作用力的理论预测和测量。通过耦合直接成像和干涉测量，我们能够测量胶体的原位接触角，并将其位置与界面曲率相关联。这种方法可以测量低至飞牛顿的极其微小的毛细力。测量结果与将毛细力与高斯曲率梯度以及胶体沉积前界面的平均曲率相关联的理论吻合良好。数值计算证实了这些结果。
