Science Friday

What’s Happening On The Slippery Surface Of Ice?

January 19, 2026

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  • The traditional explanation for ice slipperiness—a thin layer of water caused by pressure or friction—is being challenged by new computational simulations suggesting surface water molecules rearrange due to electrostatic forces from nearby surfaces, forming a soft, amorphous layer. 
  • Tribology, the science of surface interactions like friction and lubrication, was formally named in the 1960s by Peter Jost, deriving from the Greek word *tribos* meaning rubbing or sliding. 
  • New research using triboelectric nanogenerators (TENGs) can detect ice formation by sensing the charge generated as the liquid-solid contact line spreads, and this generated charge can potentially be used to melt the ice itself. 

Segments

Ice as Mineral and Slippery Question
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(00:00:03)
  • Key Takeaway: Naturally occurring ice is classified as a mineral, prompting the central question of why this ‘rock’ is slippery.
  • Summary: Ice, when naturally recurring like in a snowbank or glacier, is scientifically classified as a mineral. This classification leads to the fundamental question explored in the Science Friday episode: why is this solid substance slippery? The common answer to this question is currently under debate and scrutiny.
Defining Tribology and Origin
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(00:01:01)
  • Key Takeaway: Tribology, the science of friction, wear, and lubrication, was named in the 1960s by Peter Jost from the Greek word tribos (rubbing or sliding).
  • Summary: Tribology is the field dedicated to studying surface interactions, including friction, wear, and lubrication. The term was coined in the 1960s by Peter Jost in the UK because previous descriptors like ‘friction engineers’ were too lengthy. The word originates from the Greek term tribos, meaning rubbing or sliding.
New Theory on Ice Slipperiness
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(00:01:54)
  • Key Takeaway: New computational simulations suggest ice slipperiness results from electrostatic forces causing surface water molecules to become disordered (amorphous) rather than solely from pressure or friction-induced melting.
  • Summary: Researchers at Saarland University used powerful computer simulations to investigate ice slipperiness, finding that water molecules sense nearby surfaces via their strong electric dipoles. This sensing causes the ordered crystalline water molecules at the surface to become disordered and soft, creating a slippery amorphous layer, independent of temperature or pressure.
Wax Effect on Ski Slipperiness
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(00:05:52)
  • Key Takeaway: Ski wax reduces friction because its water-repellent nature minimizes the attractive energy between the wax surface and the disordered water molecules on the ice.
  • Summary: Ski wax functions because it is water repellent; the disordered water molecules at the ice surface are not attracted to the wax. This lack of attraction reduces the energy of interaction between the ski base and the water layer, resulting in low friction and easy sliding.
Detecting and Melting Ice Formation
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(00:07:09)
  • Key Takeaway: Triboelectric nanogenerators (TENGs) can detect ice formation by measuring charge generated as the liquid-solid contact line spreads, and this charge can be used to melt the ice.
  • Summary: Researchers at the University of Toronto developed a method using TENGs to monitor ice formation, which is critical for aircraft and drones. When water freezes, the spreading contact line between liquid and solid generates friction on the TENG, producing a measurable electrical signal. Furthermore, the generated charge can be harnessed to actively melt the ice that has formed.
Curling Rock Motion Analysis
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(00:09:04)
  • Key Takeaway: Precise sensor measurements on curling stones revealed that friction force drops significantly as speed increases, but unexpectedly rises sharply at the lowest speeds.
  • Summary: The physics of curling rocks involves tracking motion using high-precision sensors borrowed from gravity measurement experiments. Analysis confirmed that friction between the granite rock and ice decreases as speed increases. A novel finding was that friction significantly increases at the very lowest speeds, which provides new insight into how the rock curls.