Physics Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Phys Rev Lett. 2013 Jul 5;111(1):014301. doi: 10.1103/PhysRevLett.111.014301. Epub 2013 Jul 3.
We address the partial wetting of liquid drops on ultrathin solid sheets resting on a deformable foundation. Considering the membrane limit of sheets that can relax compression through wrinkling at negligible energetic cost, we revisit the classical theory for the contact of liquid drops on solids. Our calculations and experiments show that the liquid-solid-vapor contact angle is modified from the Young angle, even though the elastic bulk modulus (E) of the sheet is so large that the ratio between the surface tension γ and E is of molecular size. This finding indicates a new elastocapillary phenomenon that stems from the high bendability of very thin elastic sheets rather than from material softness. We also show that the size of the wrinkle pattern that emerges in the sheet is fully predictable, thus resolving a puzzle in modeling "drop-on-a-floating-sheet" experiments and enabling a quantitative, calibration-free use of this setup for the metrology of ultrathin films.
我们研究了液体滴在超薄固体薄片上的部分润湿问题，这些薄片位于可变形的基底上。考虑到薄片可以通过在几乎没有能量成本的情况下起皱来松弛压缩的膜极限，我们重新审视了关于液体滴在固体上接触的经典理论。我们的计算和实验表明，即使薄片的弹性体模量(E)非常大，以至于表面张力γ与 E 的比值为分子大小，液体-固体-蒸汽的接触角也会偏离杨氏角。这一发现表明了一种新的弹性毛细现象，它源于非常薄的弹性薄片的高弯曲性，而不是材料的柔软性。我们还表明，薄片中出现的皱纹图案的大小是完全可以预测的，从而解决了在“漂浮薄片上的液滴”实验建模中的一个难题，并使这种设置能够用于超薄膜的计量学，而无需进行定量校准。
