Researchers create super-repellant surface material (w/ video)

Jan 09, 2013 by Bob Yirka report
Researchers create super-repellant surface material

(Phys.org)—Researchers from the University of Michigan working in collaboration with associates from the US Air Force have created a new type of surface cover that repels oils, water, alkali solutions, acids and even non-Newtonian fluids. In their paper published in Journal of the American Chemical Society, the researchers describe their new material and the different ways it can repel various liquids.

The material they've created works due to two separate aspects: its and its physical layout. It's based on a very small gauge steel mesh which has been coated with polymer ( and POSS) beads. The unique pattern laid down limits surface area and has an overhanging structure that limits adhesion. Also, tiny air pockets between the beads prevent materials from actually touching other parts of the surface, preventing liquids from getting a grip.

The researchers explain that surface repellents work in general by limiting the wetting hysteresis – the amount of deformation that occurs when a liquid hits a surface. Ideally the at both the front and rear of a drop remain the same – the result is a lessened impact area. In practical terms this means that the more a drop remains formed like a drop when it strikes, the less likely it is to adhere to a surface.

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Credit: J. Am. Chem. Soc., Article ASAP, DOI: 10.1021/ja310517s

Researchers have found it particularly difficult to develop surface covers that repel liquids that contain polymers, particularly non-Newtonian fluids. This is because such substances tend to deform almost immediately on contact. Thus, the challenge has been to discover a way to cause such fluids to retain their shape as they drop onto a surface. With the new material, the overhanging, eave-like edges of the beads prevent the liquid drop from distending while also preventing it from reaching an adjacent part of the surface. That limits the amount of distension and thus the deformation of the drop.

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Credit: J. Am. Chem. Soc., Article ASAP, DOI: 10.1021/ja310517s

This video is not supported by your browser at this time.
Credit: J. Am. Chem. Soc., Article ASAP, DOI: 10.1021/ja310517s

The researchers demonstrated the material's ability to repel liquids by shooting various liquids through a small jet at a covered surface and filming it as it bounced off instead of adhered. They also demonstrated that the covering also provides protection from chemical attack by dunking a coated aluminum plate into several acidic solutions. Its strength in doing so, the team explains, comes about from the same properties that prevent adhesion. If an acid cannot touch a surface (because of the air pockets) it cannot destroy it.

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More information: Superomniphobic Surfaces for Effective Chemical Shielding, J. Am. Chem. Soc., Article ASAP, DOI: 10.1021/ja310517s

Abstract
Superomniphobic surfaces display contact angles >150° and low contact angle hysteresis with essentially all contacting liquids. In this work, we report surfaces that display superomniphobicity with a range of different non-Newtonian liquids, in addition to superomniphobicity with a wide range of Newtonian liquids. Our surfaces possess hierarchical scales of re-entrant texture that significantly reduce the solid–liquid contact area. Virtually all liquids including concentrated organic and inorganic acids, bases, and solvents, as well as viscoelastic polymer solutions, can easily roll off and bounce on our surfaces. Consequently, they serve as effective chemical shields against virtually all liquids—organic or inorganic, polar or nonpolar, Newtonian or non-Newtonian.

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User comments : 4

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grondilu
5 / 5 (1) Jan 09, 2013
Potential applications for this stuff are just mind-blowing.
ValeriaT
5 / 5 (2) Jan 09, 2013
It depends on how these surfaces are sensitive to mechanical abrasion or contamination.
Mike_Massen
5 / 5 (2) Jan 10, 2013
Would be a great liner for a dry toilet bowl system ;-)

Covering for electronic equipment, interested to know how well it deals with surface charges re static electricity, might it be a good material for generating static charges and especially so with fluids made of molecules with no dipoles such as benzene etc or something far less carcinogenic... is it UV stable in full sunlight to stand the 49 deg C days we get in summer in Australia !

Yeah heap of applications, cool :-)

Whats the cost, application methods etc ?
h20dr
not rated yet Jan 14, 2013
This would be incredibly useful in so many different applications if is robust and economically feasible. It would certainly help a product I work with perform better.