ASK ME PHYSICS: How can a ant walk upside down on a nano coated glass plate ?

@small1axe

Now this question is a bit vague. The problem is that "nano coated glass" can apply to a number of things. Nanotechnology refers to objects layers and structures built on a tiny scale. The scale is really small, 1 x 10-9 meters, in other words one billionth of a meter. So the coat can be doing anything on the glass surface.

What most of these coats are doing is making the glass extremely hydrophobic.

So i'm assuming the question falls in the area of how can a ant walk on a hydrophobic surface.

It is actually very simple answer. Ants walk on walls in trees etc by using tiny hairs on there legs which have hooks in them to hold them to the surface. So a rough surface is very easy to walk on and a smooth surface is very hard to walk on.

Now glass is a very smooth surface, though it appears that it is rough enough for an ant to walk up. If we treat this glass to make it hydrophobic, the treatments we are giving it do not make it smoother. The overall roughness would be the same or maybe a bit rougher.

So we have a new surface that hasnt really changed that much for the ants point of view. It has a new invisible film of substance over it that follows the rough texture of the glass below. (Like snow on a mountain)

This paper discusses that roughening the surface does affect the hydrophobic properties of a surface. Basically roughening the surface of a hydrophilic surface makes the surface more hydrophilic, and roughening the surface of a hydrphobic surface makes it more hydrophobic.
https://www.icevirtuallibrary.com/doi/pdf/10.1680/si.13.00017

So in conclusion for the ant, most nano coating is for creating a hydrophobic surface. Nano coating does not mean making it smooth down to the scale of a nanometer, it means adding a layer that is very thin to the surface of the glass. So the introduction of the layer if anything could potentially make it easier for an ant to walk up, and definitely wont make it harder.

Now for fun here's a quick talk about how a hydrophobic surface works.
we can look at the picture below.

So the simple fact of the matter is that, a hydrophobic surface is defined by surface tensions and energy. Now every surface has free energy. It is the energy that was not used to bond with more of the same material, so the higher the free energy the more energy it has to bond with something else, lets say water.
We can see this from the equation above, as the solid surface free energy gets larger, cos (theta) gets larger, and therfore the angle gets smaller.

{ cos(0) = 1 cos(90) =0 }

Now to make a hydrophobic surface more hydrophobic we roughen the surface, this means that the water has less contact with the surface and therefore is in contact with less of the free energy. so the water retains more of its shape as a sphere than flattening out.

I hope this was of help,

let me know if you have any further questions on this or anything else

The Surf Graduate