Self-Propelled Ice on Herringbones

Area of Science:

• Physics
• Materials Science
• Surface Science

Background:

• Droplets and sublimating solids exhibit self-propulsion on asymmetric surfaces via Leidenfrost ratchets.
• This phenomenon relies on viscous entrainment with underlying vapor flow.

Purpose of the Study:

• Investigate solid-liquid self-propulsion of melting ice disks.
• Extend the understanding of ratcheting phenomena to a more viscous regime.

Main Methods:

• Utilized hydrophilic and superhydrophobic herringbone surface structures.
• Observed the motion of melting ice disks on these surfaces.
• Analyzed the role of meltwater flow and Laplace pressure.

Main Results:

• Ice disks self-propelled on hydrophilic surfaces through unidirectional viscous meltwater flow.
• On superhydrophobic surfaces, ice disks initially adhered, then dislodged and moved due to Laplace pressure mismatch.
• A start-up time was required for meltwater channel filling on hydrophilic surfaces and for dislodging on superhydrophobic surfaces.

Conclusions:

• Demonstrated solid-liquid self-propulsion of melting ice disks, analogous to Leidenfrost ratchets but in a viscous regime.
• Highlighted the distinct mechanisms of self-propulsion on hydrophilic (viscous entrainment) and superhydrophobic (Laplace pressure) surfaces.
• Identified the critical role of surface wettability and geometry in controlling ice disk motion.