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.