CNST collaboration tunes viscous drag on superhydrophobic surfaces

Dec 01, 2011

(PhysOrg.com) -- By measuring the motion of a vibrating, porous membrane separating water and air, researchers from the NIST Center for Nanoscale Science and Technology, the NIST Physical Measurement Laboratory, the University of Maryland, and Boston University have revealed a new regime of fluid behavior near solid surfaces that has not been previously observed.

The research team studied the behavior of a 200 nm-thick containing a mesh of 10 µm-diameter . The surfaces of the membrane were chemically modified to repel water (superhydrophobic), and each membrane was fabricated in a device enabling it to have water on one side and air on the other. Using this novel system, the researchers observed that the friction force, or drag, on the water side is reduced dramatically when the spacing between the pores is reduced.

The researchers attribute the observed drag reduction along with an observed decrease in the mass of the water that moves along with the membrane to the formation of a stable layer of air a few tens of nanometers thick between the water and the pores. The layer forms because the large pores in the thin membrane allow air to enter freely, and the layer then decouples the membrane from the liquid.

Despite this airflow, the membrane remains a barrier to liquid water because of its hydrophobic coating. This surprising result may help explain various puzzling biofluidic phenomena and lead to better control of viscous drag in practical systems ranging from pipes, to vehicles, to atomic force microscope sensors.

Explore further: New approach to form non-equilibrium structures

More information: Porous superhydrophobic membranes: hydrodynamic anomaly in oscillating flows, S. Rajauria, O. Ozsun, J. Lawall, V. Yakhot, and K. L. Ekinci, Physical Review Letters 107, 174501 (2011).

add to favorites email to friend print save as pdf

Related Stories

Better way to desalinate water discovered

Feb 09, 2006

Chemical engineer Kamalesh Sirkar, PhD, a distinguished professor at New Jersey Institute of Technology and an expert in membrane separation technology, is leading a team of researchers to develop a breakthrough method to ...

Recommended for you

New approach to form non-equilibrium structures

1 hour ago

Although most natural and synthetic processes prefer to settle into equilibrium—a state of unchanging balance without potential or energy—it is within the realm of non-equilibrium conditions where new possibilities lie. ...

Nike krypton laser achieves spot in Guinness World Records

2 hours ago

A set of experiments conducted on the Nike krypton fluoride (KrF) laser at the U.S. Naval Research Laboratory (NRL) nearly five years ago has, at long last, earned the coveted Guinness World Records title for achieving "Highest ...

Chemist develops X-ray vision for quality assurance

7 hours ago

It is seldom sufficient to read the declaration of contents if you need to know precisely what substances a product contains. In fact, to do this you need to be a highly skilled chemist or to have genuine ...

The future of ultrashort laser pulses

7 hours ago

Rapid advances in techniques for the creation of ultra-short laser pulses promise to boost our knowledge of electron motions to an unprecedented level.

IHEP in China has ambitions for Higgs factory

Jul 23, 2014

Who will lay claim to having the world's largest particle smasher?. Could China become the collider capital of the world? Questions tease answers, following a news story in Nature on Tuesday. Proposals for ...

User comments : 0