Murata Ken-Ichiro, Asakawa Harutoshi, Nagashima Ken, Furukawa Yoshinori, Sazaki Gen
Institute of Low Temperature Science, Hokkaido University, N19-W8, Kita-ku, Sapporo 060-0819, Japan.
Phys Rev Lett. 2015 Dec 18;115(25):256103. doi: 10.1103/PhysRevLett.115.256103. Epub 2015 Dec 17.
We have experimentally determined the surface tension-to-shear viscosity ratio (the so-called characteristic velocity) of quasiliquid layers (QLLs) on ice crystal surfaces from their wetting dynamics. Using an advanced optical microscope, whose resolution reaches the molecular level in the height direction, we directly observed the coalescent process of QLLs and followed the relaxation modes of their contact lines. The relaxation dynamics is known to be governed by the characteristic velocity, which allows us to access the physical properties of QLLs in a noninvasive way. Here we quantitatively demonstrate that QLLs, when completely wetting ices, have a thickness of 9±3 nm and an approximately 200 times lower characteristic velocity than bulk water, whereas QLLs, when partially wetting ices, have a velocity that is 20 times lower than the bulk. This indicates that ice crystal surfaces significantly affect the physical properties of QLLs localized near the surfaces at a nanometer scale.
我们通过准液体层（QLLs）在冰晶表面的润湿动力学实验测定了其表面张力与剪切粘度之比（即所谓的特征速度）。使用一台先进的光学显微镜，其在高度方向上的分辨率达到分子水平，我们直接观察了QLLs的聚并过程，并跟踪了它们接触线的弛豫模式。已知弛豫动力学由特征速度控制，这使我们能够以非侵入性方式获取QLLs的物理性质。在此我们定量证明，当QLLs完全润湿冰时，其厚度为9±3 nm，特征速度比 bulk water 低约200倍；而当QLLs部分润湿冰时，其速度比 bulk water 低20倍。这表明冰晶表面在纳米尺度上显著影响了位于表面附近的QLLs的物理性质。
