Superhydrophobic Paper
Taking inspiration from the water repelling qualities of lotus leaves researchers Lester Li, Victor Breedveld and Dennis Hess of Georgia Institute of Technology have come up with a superhydrophobic paper that has been proven to repel most liquids and oils. The paper is made from standard softwood and hardwood fibers. The fibers then undergo the standard manufacturing process where the cellulose in them in broken down into smaller parts by mechanical grinding. In the conventional way the paper is pressed in presence of water, but while making this paper the water is removed and butanol is added instead. Butanol inhibits the hydrogen bonding that normally takes place between cellulose allowing better control of their spacing.
In the next step, the researchers used an oxygen plasma etching process to remove the layer of ‘fluffy’ cellulose layer to expose the ‘rougher’ layer of crystalline cellulose nanofibrils on which a thin coating of a fluoropolymer is applied to give it the liquid repelling capability. During the testing process the paper was able to repel water, motor oil, ethylene glycol and n-hexadecane solvent. Researchers have also managed to print patterns on the paper using a hydrophobic ink and a desktop printer. The liquid droplets adhered to the ink pattern and were repelled by the rest of the paper. The team hopes to see that their invention could lead to the development of inexpensive biomedical diagnostic tests where a droplet of liquid containing antigens can be rolled on to printed surface where it would be in contact with diagnostic chemicals and depending upon the reagents they would help identify the disease.
You might have already read about the Superomniphobic Layer developed by the University of Michigan but the difference between both is flexibility. The paper version is very flexible and to some extent cheaper than its predecessor.
For more details of the project, head over to Georgia Tech.
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