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.