Introduction: Superhydrophobic Surfaces Based on PDMS Microstructures

Super–hydrophobic surfaces

The aim of this project is to study super-hydrophobic surfaces and their behavior.

Super-hydrophobic surfaces (SHS) are surfaces which result in contact angles of water on theses surfaces of greater than 150° in conjunction with shallow sliding angles, α. [1]

SHS are very useful and their applications span a broad range including such diverse applications as in the aerospace industry where they are used to minimize aerodynamic drag or keep the aerodynamic surfaces ice free and the medical industry where they are used on/in artificial, insertables for minimization of the clotting cascade or fouling.

Super-hydrophobic materials rely on a composite interface of different contact angles as demonstrated by Cassie's law; essentially, all things been equal, a rougher surface allows for a much higher apparent contact angle than one that has the same composition but a smoother surface.

In nature, this behavior is often describe as Lotus effect, and it is use by plants for self cleaning purpose, and in case of carnivorous plants, feeding.

In order to create these type of surface structures, we will create 4 different masks (they can be all be on the same substrate). The masks will be a square array of square features. The size of the features and the lattice constant will be varied for each mask. We expect the characteristic dimensions to be in the range of 10 to 500 microns. Using the mask set and varying the height of the etched features (through etching or starting thickness) will allow for a small set of molds for soft lithographic patterning in PDMS surfaces. Another dimension will be added to this matrix in that chemical, such as 1H,1H,2H,2H-perfluorooctyl treatment, or plasma (oxygen) of the PDMS creating a four dimensional test. Because of the large ensuing matrix size, we shall probably employ an optimized DEO (design of experiment.)

In the experiment, the effective contact angle, the sliding angle and the velocity of shedding will be analyzed.

Comments

author
BuffaloFan32 (author)2015-02-23

Is this related to this:

http://www.rochester.edu/newscenter/superhydrophob...

Is this something that an at-home novice like me can study?

author
gcannici (author)BuffaloFan322015-02-23

yes it is related to that, there are a lot of studies on superhydrophobicity, and in general on wettability, have a look to this studies too:

http://wyss.harvard.edu/viewpage/99/adaptive-archi...

http://aizenberglab.seas.harvard.edu/index.php?show=research_topic&top=4

author
gcannici (author)2015-02-23

Hi!

No I am sorry, for repeating the same exercise you need a clean room. What you can do is molding a lotus leaf with PDMS (which is not dangerous, see link below), you won't be able to treat the PDMS by silanization, but the texture of leaf should give you some decent hydrophobicity, just make sure you pour the PDMS very slowly to avoid bubbles. If you don't have a vacuum chamber you can burst the bubbles on the surface with an air compressor.

Hope it helps, let me know how it goes.

Best

Giorgia

http://en.wikipedia.org/wiki/Polydimethylsiloxane

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