MIT creates new oil-repelling material

Dec 06, 2007
MIT creates new oil-repelling material
A steel mesh coated with a polymer containing a low concentration of a synthesized molecule called fluoroPOSS can repel water (dyed blue) but attracts the flammable fuel hexadecane (dyed red), allowing it to be used to separate the two substances. Photo / Anish Tuteja and Wonjae Choi, courtesy Science

MIT engineers have designed the first simple process for manufacturing materials that strongly repel oils. The material, which can be applied as a flexible surface coating, could have applications in aviation, space travel and hazardous waste cleanup.

For example, the material could be used to help protect parts of airplanes or rockets that are vulnerable to damage from being soaked in fuel, such as rubber gaskets and o-rings.

“These are vulnerable points in many aerospace applications” said Robert Cohen, the St. Laurent Professor of Chemical Engineering and an author of a paper on the work that will appear in the Dec. 7 issue of Science.

“It would be nice if you could spill gasoline on a fabric or a gasket or other surface and find that instead of spreading, it just rolled off,” Cohen said.

Creating a strongly oil-repelling, or “oleophobic” material, has been challenging for scientists, and there are no natural examples of such a material.

“Nature has developed a lot of methods for waterproofing, but not so much oil-proofing,” said Gareth McKinley, MIT School of Engineering Professor of Teaching Innovation in the Department of Mechanical Engineering and a member of the research team. “The conventional wisdom was that it couldn't be done on a large scale without very special lithographic processes.”

The tendency of oils and other hydrocarbons to spread out over surfaces is due to their very low surface tension (a measure of the attraction between molecules of the same substance).

Water, on the other hand, has a very high surface tension and tends to form droplets. For example, beads of water appear on a freshly waxed car (however, over a period of time, oil and grease contaminate the surface and the repellency fades). That difference in surface tension also explains why water will roll off the feathers of a duck, but a duck coated in oil must be washed with soap to remove it.

The MIT team overcame the surface-tension problem by designing a material composed of specially prepared microfibers that essentially cushion droplets of liquid, allowing them to sit, intact, just above the material's surface.

When oil droplets land on the material, which resembles a thin fabric or tissue paper, they rest atop the fibers and pockets of air trapped between the fibers. The large contact angle between the droplet and the fibers prevents the liquid from touching the bottom of the surface and wetting it.

The microfibers are a blend of a specially synthesized molecule called fluoroPOSS, which has an extremely low surface energy, and a common polymer. They can be readily deposited onto many types of surfaces, including metal, glass, plastic and even biological surfaces such as plant leaves, using a process known as electrospinning.

The researchers have also developed some dimensionless design parameters that can predict how stable the oleophobicity or oil-resistance between a particular liquid and a surface will be. These design equations are based on structural considerations, particularly the re-entrant nature (or concavity) of the surface roughness, and on three other factors: the liquid's surface tension, the spacing of the fibers, and the contact angle between the liquid and a flat surface.

Using these relationships, the researchers can design fiber mats that are optimized to repel different hydrocarbons. They have already created a non-woven fabric that can separate water and octane (jet fuel), which they believe could be useful for hazardous waste cleanup.

The Air Force, which funded the research and developed the fluoroPOSS molecules, is interested in using the new material to protect components of airplanes and rockets from jet fuel.

Source: Massachusetts Institute of Technology

Explore further: New research predicts when, how materials will act

add to favorites email to friend print save as pdf

Related Stories

Why can't we design the perfect spacesuit?

Feb 19, 2015

So far, every spacesuit humans have utilized has been designed with a specific mission and purpose in mind. As of yet, there's been no universal or "perfect" spacesuit that would fit every need. For example, ...

Kitchen sponge supercapacitor has many porous benefits

Feb 06, 2015

By dipping small pieces of an ordinary kitchen sponge into solutions of nanoscale electrode materials, scientists have created a light-weight, low-cost supercapacitor that benefits from the sponge's porous ...

Preventing greenhouse gas from entering the atmosphere

Feb 05, 2015

A novel class of materials that enable a safer, cheaper, and more energy-efficient process for removing greenhouse gas from power plant emissions has been developed by a multi-institution team of researchers. ...

Recommended for you

Precision gas sensor could fit on a chip

49 minutes ago

Using their expertise in silicon optics, Cornell engineers have miniaturized a light source in the elusive mid-infrared (mid-IR) spectrum, effectively squeezing the capabilities of a large, tabletop laser onto a 1-millimeter ...

A new X-ray microscope for nanoscale imaging

1 hour ago

Delivering the capability to image nanostructures and chemical reactions down to nanometer resolution requires a new class of x-ray microscope that can perform precision microscopy experiments using ultra-bright ...

New research signals big future for quantum radar

13 hours ago

A prototype quantum radar that has the potential to detect objects which are invisible to conventional systems has been developed by an international research team led by a quantum information scientist at the University ...

Top-precision optical atomic clock starts ticking

16 hours ago

A state-of-the-art optical atomic clock, collaboratively developed by scientists from the University of Warsaw, Jagiellonian University, and Nicolaus Copernicus University, is now "ticking away" at the National ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Chemijim
1 / 5 (1) Dec 07, 2007
The caption for the photo appears incorrect. The material should ATTRACT water and REPEL oil if it's made of fluoroPOSS. The caption for the photo states the opposite, and water repellent fabric is nothing new.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.