 |
|
MIT creates new oil-repelling material
December 07, 2007Many applications in aviation, more
CAMBRIDGE, Mass.--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.
Massachusetts Institute of Technology
"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.
Massachusetts Institute of Technology
Surface Tension News and Current Surface Tension Events RSSMelting defects could lead to smaller, more powerful microchips
As microchips shrink, even tiny defects in the lines, dots and other shapes etched on them become major barriers to performance. Princeton engineers have now found a way to literally melt away such defects, using a process that could dramatically improve chip quality without increasing fabrication cost.
Nanoemulsion vaccines show increasing promise
A novel technique for vaccinating against a variety of infectious diseases - using an oil-based emulsion placed in the nose, rather than needles - has proved able to produce a strong immune response against smallpox and HIV in two new studies.
'Electrospray' droplet research yields surprising, practical results
Chemical engineers at Purdue University are the first to mathematically describe precisely how droplets form when liquids are exposed to electric fields, an advance that could have applications in areas ranging from manufacturing to medical diagnostics.
ORNL super water repellent could cause big wave in market
A water repellent developed by researchers at the Department of Energy's Oak Ridge National Laboratory outperforms nature at its best and could open a floodgate of commercial possibilities.
Inhaled nitric oxide safe for tiny preemie lungs, UCSF study finds
A nationwide study led by researchers at UCSF provides evidence that inhaled nitric oxide is safe and effective for the prevention of the most common type of long-term lung disease of very premature infants.
Case closed: MIT gumshoes solve
Hey kids! Try this at home. Pour clean water onto a small plate. Wait for all the ripples to stop.
Ground breaking research to end in tears
University of Western Sydney researcher, Associate Professor Tom Millar has approached the problem of dry eyes from a new perspective. He re-examined the structure and function of natural tears to find new clues for creating longer lasting artificial tears.
Wetter report: New approach to testing surface adhesion
With a nod to one of nature's best surface chemists—an obscure desert beetle—polymer scientists at the National Institute of Standards and Technology (NIST) have devised a convenient way to construct test surfaces with a variable affinity for water, so that the same surface can range from superhydrophilic to superhydrophobic, and everything in between.
Physicist: Stars can be strange
According to the "Strange Matter Hypothesis," which gained popularity in the paranormal 1980's, nuclear matter, too, can be strange.
Ferns provide model for tiny motors powered by evaporation
Scientists looked to ferns to create a novel energy scavenging device that uses the power of evaporation to move itself - materials that could provide a method for powering micro and nano devices with just water or heat.
More Surface Tension News Articles
 | Incompressible Flow by Ronald L. Panton Incompressible Flow, Third Edition is the updated and revised edition of Ronald Panton’s classic text on fluid mechanics. Beginning with basic principles, this Third Edition patiently develops the math and physics leading to major theories. The book provides a unified presentation of physics, mathematics, and engineering applications, along with a liberal supplement of helpful exercises and... |
 | Soap Bubbles: Their Colors and Forces Which Mold Them by C. V. Boys Consists of dozens of experiments, explanations of the principles they demonstrate, and detailed discussions of the color and thickness of soap bubbles. Shows how liquid films, surface tension, and related phenomena react to heat, motion, music, more. 1911... |
 | Surface Tension by Christine Kling In a stunning debut novel featuring a resourceful female amateur P.I., Christine Kling establishes herself as a major voice in suspense fiction. Surface Tension depicts a world as deceptive as a Florida land deal, as electrifying as the hottest Miami nightclub, and as dangerous as the tug of an invisible riptide. . . .SURFACE TENSIONYears ago Seychelle Sullivan had the chance to save a... |
 | The Mathematics of Soap Films: Explorations With Maple (Student Mathematical Library, Vol. 10) (Student Mathematical Library, V. 10) by John Oprea Nature tries to minimize the surface area of a soap film through the action of surface tension. The process can be understood mathematically by using differential geometry, complex analysis, and the calculus of variations. This book employs ingredients from each of these subjects to tell the mathematical story of soap films. The text is fully self-contained, bringing together a mixture of types... |
 | Surface and Interfacial Tension: Measurement, Theory, and Applications (Surfactant Science) This edited volume offers complete coverage of the latest theoretical, experimental, and computer-based data as summarized by leading international researchers. It promotes full understanding of the physical phenomena and mechanisms at work in surface and interfacial tensions and gradients, their direct impact on interface shape and movement, and their significance to numerous applications.... |
 | Surface Tension: Love, Sex and Politics Between Lesbians and Straight Women by Meg Daly Representing a fascinating spectrum of feelings and opinions about lesbianism, the friendships women share -- or fear -- and the rich diversity of personal choices women make today, this collection of brash and thoughtful essays, stories, and interviews offers-- Dorothy Allison on what it means to be a lesbian-- Carla Trujillo on the impact of "sexual betrayal" by an ex-lover-- Elizabeth Wurtzel... |
 | Surface Tension by Elaine Equi |
 | Capillary Forces in Microassembly: Modeling, Simulation, Experiments, and Case Study (Microtechnology and MEMS) by P. Lambert Capillary Forces in Microassembly discusses the use of capillary forces as a gripping principle in microscale assembly. Clearly written and well-organized, this text brings together physical concepts at the microscale with practical applications in micromanipulation. Throughout this work, the reader will find a review of the existing gripping principles, elements to model capillary forces as well... |
 | Surface Treatment of Materials for Adhesion Bonding by Sina Ebnesajjad This is a unique compilation of surface preparation principles and techniques for plastics, thermosets, elastomers, and metals bonding. With emphasis on the practical, it draws together in a single source technical principles of surface science and surface treatments technologies of plastics, elastomers, and metals. It is both a reference and a guide for engineers, scientists, practitioners of... |
 | Surface Tension: Problematics of Site "From Gordon Matta-Clark to Lawrence Weiner, Bruce Nauman to Alison Knowles, the question of site locates itself in issues of public space, at the intersection of the imagined and the real, at the juncture of performance and architectural production. By anthologizing essays, documents, and interviews by leading critics, historians, and artists on issues of site-specificity, conceptualism,... |
| © 2008 BrightSurf.com |