During ice crystal (snowflake) formation, the synchronization of branch growth occurs due to the interaction with the medium (oversaturated vapor) – is somewhat similar to the hydrophobic effect – the apparent repulsion of the hydrophobic particles due to their interaction with the medium (water).
[7] Note that thermodynamically both the hydrophobic interactions and ice formation are driven by the minimization of the surface Gibbs energy, ΔG = ΔH − TΔS, where H, T, and S are the enthalpy, temperature, and entropy, respectively.
The so-called surface roughening transition governs the direction of ice crystal growth and occurs at the critical temperature, above which the entropic contribution into the Gibbs energy, TΔS, prevails over the enthalpic contribution, ΔH, thus making it more energetically profitable for the ice crystal to be rough rather than smooth.
Third, the icephobic surfaces should repel incoming small droplets (e.g., of rain or fog) at the temperatures below the freezing point.
[12] These three definitions imply that icephobic surfaces should (i) prevent freezing of water condensing on the surface (ii) prevent freezing of incoming water (iii) if ice formed, it should have weak adhesion strength with the solid, so that it can be easily removed.
Mechanical properties of ice and the substrate also of great importance since ice shedding occurs as fracture, either in the Mode I (normal) or Mode II (shear) cracking, so that crack concentrators are major contributors to the reduced strength.