Inside Rensselaer
Volume 7, No. 15, October 11, 2013

Water Glides Across “Nanodrapes” Made From the World’s Thinnest Material

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Covering the surface of a material with an impermeable graphene drape prevents a droplet from getting pinned to the surface.

Engineering researchers at Rensselaer have developed a new drape made from graphene—the thinnest material known to science—which can enhance the water-resistant properties of materials with rough surfaces.

These “nanodrapes” are less than a nanometer thick, chemically inert, and provide a layer of protection without changing the properties of the underlying material. The team of researchers, led by Rensselaer Professor Nikhil Koratkar, demonstrated how droplets of water encounter significantly less friction when moving across a surface covered with a nanodrape.

This innovation holds the potential to benefit lab-on-chip devices, high-throughput assays, self-cleaning surfaces, and many other applications requiring the motion of liquid drops on solid surfaces.

“Graphene nanodrapes are the thinnest, most sheer drapes we can imagine. Other than providing a barrier against water, these drapes are optically transparent and cause minimal changes to the topology of the underlying surface,” said Koratkar, the John A. Clark and Edward T. Crossan Professor of Engineering. “We found this ultrasheer drape prevents the penetration of water into textured surfaces, which has interesting and potentially important technological implications for many applications in micro- and nanofluidics.”

Drops of water can get easily stuck or “pinned” to a material with a nanotextured rough surface. When the droplet falls onto the material, the energy from the fall pushes out or displaces the tiny amounts of air trapped in the textured surface. Once in this pinned state, it is difficult to unpin the droplet and move it around.

Covering the surface with an impermeable graphene drape, however, prevents a droplet from getting pinned to the surface. The nanodrape creates a barrier that prevents the water drop from penetrating into and displacing the air from the textured surface. Instead, the droplet sits on top of the drape, with reduced friction between them, which in turn makes it easier to move the droplet around on the surface, Koratkar said. While helping to minimize this friction, the ultrasheer nanodrape causes minimal disruption to the underlying surface.

Along with Koratkar, co-authors of the paper are: Yoav Peles, professor in MANE; Yunfeng Shi, assistant professor in MSE; Rensselaer postdoctoral researcher Farzad Houshmand; and Rensselaer graduate students Eklavya Singh, Abhay Thomas, Rahul Mukherjee, and Xi Mi.

The study was funded by the Office of Naval Research and the National Science Foundation, with support from Koratkar’s John A. Clark and Edward T. Crossan Endowed Chair Professorship.ribosomes, which manufacture proteins for living cells. Statistically, there could be as many as 256 possible sequences of those four bases, but only three sequences actually appear in tetraloops. Once formed, they are highly stable, outlasting other structures when subjected to the destructive force of increasing heat.

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Inside Rensselaer
Volume 7, Number 15, October 11, 2013
Rensselaer Polytechnic Institute
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