Background: Typical, everyday paper (newspaper, writing paper, etc.) is a cellulose-based paper made from wood fibers that have been dried from a suspension in water and pressed into a flat sheet. This kind of paper is both hydrophilic and oleophilic, meaning it readily absorbs both oil and water. Certain applications, such as biochemical assays, could benefit from a surface that repels water (hydrophobic), oil (oleophobic), or both. Currently, paper is coated with layers of waxes or polymers in order to make it hydrophobic/oleophobic, however these coatings can degrade over time and may cause undesirable properties to the paper. Creating other hydrophobic/oleophobic surfaces requires adding an array of nail head-shaped nanostructures using a complex lithographic process, but this approach is not cost effective and requires special materials. Paper can be produced inexpensively and is flexible and strong- therefore, there is a need for a superamphiphobic paper and a method of making it.
Technology: Dennis Hess, Laurens Breedveld, and Lester Li from the School of Chemical and Biomolecular Engineering at Georgia Tech have produced a cellulose based paper substrate that are both superhydrophobic and superoloephobic. The superomniphobic paper is made by using a solvent exchange process, where the water in the pulp is replaced with sec-butanol. The butanol prevents hydrogen bonding between individual fibers, which allows the necessary fiber spacing to support oil droplets. The solvent process establishes the necessary structure to support high contact angles greater than 150 degrees, which is a significant improvement over current paper coating technologies. This technology also has the ability for variations and modifications without departing from the basic concept presented here.
Potential Commercial Applications: This technology has applications in paper based packaging and fiber based oil proof surfaces. Also, there is potential in the bioassay/biopharmaceutical industry- A superamphiphobic sheet with a region of functional molecules could be used to detect the presence of antibodies or disease from blood samples.
· Cost effective
· Has a higher oil repellency than currently available
· Can be modified to repel other substances
· Paper is durable and strong- making it more functional than other omniphobic surfaces