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: How the physics of champagne bubbles may help address the world's future energy needs

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

What's next for the Large Hadron Collider?

Dec 17, 2014

The world's most powerful particle collider is waking up from a well-earned rest. After roughly two years of heavy maintenance, scientists have nearly doubled the power of the Large Hadron Collider (LHC) ...

User comments : 0

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.