Article Highlight | 6-Nov-2025

The coupled impact-freezing mechanism of supercooled droplet on superhydrophobic surface

Shanghai Jiao Tong University Journal Center

Diagram of the impact-freezing model of supercooled water droplet for superhydrophobic surface

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  1. This diagram presents a theoretical model for droplet impact-freezing on superhydrophobic surfaces. It contrasts two distinct dynamic behaviors: on rough surfaces, droplets spread, break up during retraction, and ultimately form a stationary spherical droplet; whereas on smooth surfaces, droplets complete retraction and fully rebound.
  2. The model establishes key timelines for both nucleation and ice growth phases, defining critical moments including nucleation time, horizontal ice formation fixation, and complete freezing. The sequence of these events relative to the droplet's dynamic motion determines the final outcome.
  3. The model provides clear morphological criteria based on the timing of nucleation relative to retraction completion. If nucleation occurs before retraction finishes, irregular hill-shaped ice forms. If nucleation happens after retraction completes, spherical ice forms on rough surfaces while no ice remains on smooth surfaces due to droplet rebound.
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Credit: Haocheng Wu,Weiliang Kong,Peixiang Bian,Hong Liu.

As the demand for efficient anti-icing solutions in aerospace and other fields grows, the inconsistent performance of conventional superhydrophobic coatings under supercooled conditions remains a critical challenge. A pivotal study from a research team at  Shanghai Jiao Tong University has now uncovered the coupled mechanism of droplet impact and freezing on these surfaces. Their work provides a fundamental blueprint for designing next-generation, high-performance anti-icing surfaces.

Why the Coupling Mechanism is a Game-Changer:

Morphology Redefined: The study reveals for the first time that the final ice morphology is determined not by contact angle, but by surface roughness, challenging conventional understanding.

The Core Competition:The interplay between the rapid retraction of unfrozen water  and the timing of ice nucleation is the key factor dictating freezing morphology and size.

A Performance Divide:Rough and smooth superhydrophobic surfaces exhibit drastically different freezing behaviors, explaining the variable performance of existing coatings.

Key Findings and Theoretical Breakthroughs:

Two Dynamic Modes: The team identified two distinct droplet motion modes: receding break-up and convergence on rough surfaces vs. complete rebound on smooth surfaces.

Nucleation Control: Rough surfaces effectively delay nucleation, allowing droplets to freeze after retraction is complete, resulting in a neat spherical ice shape.

Multinucleation Effect: The research quantified how multiple ice nuclei accelerate freezing and introduced a correction factor (k=1.935) to accurately model this phenomenon.

Future Applications & Design Principles:

Predictive Power: A new theoretical impact-freezing model was established, capable of reliably predicting the average frozen spreading ratio on different superhydrophobic surfaces.

Design Guidelines:The study concludes that an ideal anti-icing surface should combine a smooth morphology (to promote rebound) with nucleation hysteresis ability (to delay freezing).

Broad Relevance:These insights are critical for advancing anti-icing technology in aviation, wind power, and power transmission lines.

This research from Shanghai Jiao Tong University represents a crucial step from empirical anti-icing towards theoretically-driven design. Stay tuned for more groundbreaking work from this team.

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