# Nanorheology of interfacial water during ice gliding

## TL;DR

This study investigates the microscopic rheological properties of interfacial water during ice gliding, revealing complex visco-elastic behavior that explains ice slipperiness and impacts winter sports and lubricant design.

## Contribution

The paper introduces a novel stroke-probe force measurement technique to directly measure the mechanical properties of interfacial water during ice friction, uncovering its complex rheology.

## Key findings

- Interfacial meltwater exhibits visco-elastic rheology with high viscosity.
- Hydrophobic coatings significantly reduce friction by altering local viscosity.
- The rheological properties of meltwater explain the phenomenon of ice slipperiness.

## Abstract

The slipperiness of ice is an everyday-life phenomenon which, surprisingly, remains controversial despite a long scientific history. The very small friction measured on ice is classically attributed to the presence of a thin self-lubricating film of meltwater between the slider and the ice. But while the macroscale friction behavior of ice and snow has been widely investigated, very little is known about the interfacial water film and its mechanical properties. In this work, we develop a stroke-probe force measurement technique to uncover the microscopic mechanisms underlying ice lubrication. We simultaneously measure the shear friction of a bead on ice and quantify the in-situ mechanical properties of the interfacial film, as well as its thickness, under various regimes of speed and temperature. In contrast with standard views, meltwater is found to exhibit a complex visco-elastic rheology, with a viscosity up to two orders of magnitude larger than pristine water. The non-conventional rheology of meltwater provides a new, consistent, rationale for ice slipperiness. Hydrophobic coatings are furthermore shown to strongly reduce friction due to a surprising change in the local viscosity, providing an unexpected explanation for waxing effects in winter sports. Beyond ice friction, our results suggest new avenues towards self-healing lubricants to achieve ultra-low friction.