Observation of a Large Slip Effect in the Nanoscale Flow of Highly Viscous Supercooled Liquid Metals

Understanding and controlling the flow of materials confined
in
channels play important roles in science and engineering. The general
no-slip boundary condition will result in it being more challenging
to drive the flow as the channel size decreases to the nanoscale,
especially for highly viscous liquids. Here, we report the observation
of a large boundary slip in the nanoscale flow of highly viscous supercooled
liquid metals (with viscosities of ≲108 Pa s), enabled
by the hydrophobic treatment of smooth nanochannels. The slip length
significantly depends on the pressure, which can be rationalized by
the shear-dependent viscosity. Our findings provide not only new insights
into the field of nanofluidics but also a practical technique for
resolving the challenge in the net formation of highly viscous supercooled
liquid metals at the nanoscale.

理解并调控受限通道内的物质流动，在科学与工程领域均具有重要意义。当通道尺寸缩减至纳米尺度时，普遍适用的无滑移边界条件（no-slip boundary condition）会使得流体驱动难度显著提升，对于高黏度流体而言尤为突出。本研究通过对光滑纳米通道（nanochannels）实施疏水改性（hydrophobic treatment），成功观测到黏度约≤10^8 Pa·s的高黏度过冷液态金属（supercooled liquid metals）在纳米尺度流动中的显著边界滑移（boundary slip）现象。滑移长度（slip length）显著依赖于系统压力，这一规律可通过剪切依赖黏度（shear-dependent viscosity）得到合理解释。本研究的发现不仅为纳米流体学（nanofluidics）领域提供了全新的学术视角，同时也为解决纳米尺度下高黏度过冷液态金属的净成型难题提供了实用技术方案。