Be it Metal or Glass surface , after experimenting with FAS 17 Functionalised SiO2 Particles , Coilloidal particles in various solvents , TiO2 particles , FD_POSS etc Shall I conclude that inorder to get surface roughness and Superhydrophobicity i have to trade off 'Transparency' & Durability ?
Although there are some papers that claim to be transparent but the method was facile NOT at all .It was lacked simplicity and moreover durability .Also they have harsh synthetic conditions (e.g., etching and high temperature) which not within reach of most of the labs across underdeveloped countries .
Don't we have a literature which is truly marvelous in terms of 98 % Transparency and Yet excellent durability for superhydrophobicity across surfaces.
If there is a literature that you know of that provides excellent Durability , Transparency and Superhydrophobicity across multiple substrates.Lets commend a genius among us .
Hi Rohit,
I assume that you have tried a lot of processes so far but did not manage to obtain the results you wanted. I have previously worked with FAS17 coatings on glass and silicon (using silanes) and obtained reproducible 120deg of contact angle whilst maintaining a high transparency (on glass >90%). So I might be able to provide some insight.
The maximum contact angle for a flat surface that you can get is 120 deg. That is indeed very hydrophobic. But for higher contact angles (i.e. >120deg) it is necessary to have some sort of roughness. When introducing roughness into the samples, it will cause some light scattering, and this can contribute significantly to a decrease in the transmission spectra of the sample. The degree of this light scattering will depend on the material and shape of this roughened layer. I hope this comment helped with your question on transparency trade off.
Regarding your comment on durability. If you are using a FAS17 silane (as an example) the durability depends on how you activated the surface, how strong is your bond with the surface, how dense is your silane layer, how crosslinked is your silane, and how protected is the bond from the environment. Let's explain this in more detail. Surface activation is typically performed with piranha or O2 plasma. This pretreatment increases OH groups on the surface that can react with the silane, and is suitable for materials such as metal oxides, glass and silicon. Existence of OH groups can be checked with IR spectroscopy. If that step is OK, then durability has to do with how densely packed is your hydrophobic layer, adhesion or hydrolysis. Liquid deposition of silanes is normally OK, but if highly dense layers are needed, then vapor deposition is the way to go (vapor also results in smoother coatings). Regarding adhesion, it is common to have physisorbed silane rather than covalently attached silane, covalent bonding typically occurs upon dehydration, so baking the sample at 100degC does improve the quality and resistance of silane coatings. Another way to improve adhesion is by increasing the number of bonds with the surface per molecule. For that purpose dipodal silanes increase coating durability considerably. Regarding hydrolysis, you need to protect the bond from being attacked by environmental conditions. Baking also helps to induce cross linking between adjacent silane molecules, which helps protecting the bonds from hydrolysis. Finally dimethylsilanes provide another mean to protect from hydrolysis by sacrificing to reactive groups for a dimethyl group. I hope this helps with durability.
Regards,
Gerard
Hi Rohit,
I assume that you have tried a lot of processes so far but did not manage to obtain the results you wanted. I have previously worked with FAS17 coatings on glass and silicon (using silanes) and obtained reproducible 120deg of contact angle whilst maintaining a high transparency (on glass >90%). So I might be able to provide some insight.
The maximum contact angle for a flat surface that you can get is 120 deg. That is indeed very hydrophobic. But for higher contact angles (i.e. >120deg) it is necessary to have some sort of roughness. When introducing roughness into the samples, it will cause some light scattering, and this can contribute significantly to a decrease in the transmission spectra of the sample. The degree of this light scattering will depend on the material and shape of this roughened layer. I hope this comment helped with your question on transparency trade off.
Regarding your comment on durability. If you are using a FAS17 silane (as an example) the durability depends on how you activated the surface, how strong is your bond with the surface, how dense is your silane layer, how crosslinked is your silane, and how protected is the bond from the environment. Let's explain this in more detail. Surface activation is typically performed with piranha or O2 plasma. This pretreatment increases OH groups on the surface that can react with the silane, and is suitable for materials such as metal oxides, glass and silicon. Existence of OH groups can be checked with IR spectroscopy. If that step is OK, then durability has to do with how densely packed is your hydrophobic layer, adhesion or hydrolysis. Liquid deposition of silanes is normally OK, but if highly dense layers are needed, then vapor deposition is the way to go (vapor also results in smoother coatings). Regarding adhesion, it is common to have physisorbed silane rather than covalently attached silane, covalent bonding typically occurs upon dehydration, so baking the sample at 100degC does improve the quality and resistance of silane coatings. Another way to improve adhesion is by increasing the number of bonds with the surface per molecule. For that purpose dipodal silanes increase coating durability considerably. Regarding hydrolysis, you need to protect the bond from being attacked by environmental conditions. Baking also helps to induce cross linking between adjacent silane molecules, which helps protecting the bonds from hydrolysis. Finally dimethylsilanes provide another mean to protect from hydrolysis by sacrificing to reactive groups for a dimethyl group. I hope this helps with durability.
Regards,
Gerard
The paper I attached from my old group addresses several of your comments about ease of attachment and durability. Its designed as iceophobic but its properties are super or nearly superhydrophobic under most conditions.
For translucancy, its certainly premature to say that its impossible, but it is certainly difficult. Superhydrophobicity arises from a defined degree of heterogeneity, and heterogeneous surfaces tend to scatter light.
Article Permanently Grafted Icephobic Nanocomposites with High Abras...
There are publications (pls see, e.g. http://www.sciencedirect.com/science/article/pii/S0169433215013495) where it is stated that such coatings are possible.
HI Mikhail,
The publication that you mentioned has weak durability .Understood that its facile method and doesn't require much of lab setup but if we can durability element to such publications (http://www.sciencedirect.com/science/article/pii/S0169433215013495) , it will be a great invention indeed.
Jeremy,
Thank you for research work .I will go through it .
Gerard,
Please accept my appreciation for enlightening me .Its was a good read.
Some co-workers of mine work on wettability tuning and have transparent superhydrophobic coatings, look e.g. at this paper:
http://pubs.acs.org/doi/abs/10.1021/nl5041836
where we helped them with the functionalization of their coatings, but you can also find much work if you follow up their work. Not sure about the easeness of their coating process in your eyes, but you might want to have a look!
- Badges
- Science topic
- Similar topics
- Chemistry