Antifouling paints

hi all I have been doing research on antifouling paints since one and half year. During my literature surveys I have seen lot of people working
on coating with low surface energy are efficient in getting fouling off the surface of boats. I have also read about the lotus leaf effect and i am curious to know how is lotus leaf effective? And will this lotus leaf effect work when the leaf is within the water like the surface of boats. Low surface energy materials are considered to have low adhesion to surfaces. Well I believe that coating with low surface energy will also depend on the medium that is the surrounding where it is present.
Well I have made a surface which has a contact angle of water about 145 degrees. But it is a rough surface and I am curious to know how well it will work as a antifouling paint.
thanks Rahul Agnihotri
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snipped-for-privacy@gmail.com wrote:

I think this is the 'old' approach. Of course silicones are somewhat effective, esp. if you include self polishing, but proteins tend to adsorb on hydrophobic surfaces (by denaturation etc.). The current research is more directed towards hydrophilic surfaces which prevent specific interaction of the microorganisms to the surface.

In simple terms: the lotus effect(tm) works by substituting some of the contact area fluid-surface for fluid-air contacts. The leaf surface contains waxy bumps which reduce significantly the interaction energy (contact only on the top of the bumps).

No, the lotus effect will not work under water.

Yes. You always have to consider three interactions: solid-liquid, solid-surrounding medium (usually air), liquid-surrounding medium. If you have two liquids it is possible than one will displace the other from the surface effectively, thereby eliminating any wetting of the other liquid. In air both liquids would completeley wet the surface.

I would be surprised if it worked. The ordinary lotus surface is mechanically not very stable. for the lotus this is not a problem, as it can rebuild the surface. Additionally the lotus effect does not work when the liquid has a surface tension lower than the critical surface tension of the coating. For simple waxes this can be done with every detergent solution. Even for fluorocarbons stains can be produced with organic oils, e.g. coffee, if they have a chance to dry on the surface.
In my personal opinion, if you want to achieve a real breakthrough, forget the contact angle and try to minimize the contact angle hysteresis instead.
Regards,         Oliver
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