How slippery are water-repellent surfaces? (w/ Video)

September 13, 2013

Scientists at Aalto University have measured the low but non-zero friction of droplets moving on slippery water-repellent surfaces.

In their article published in Nature Communications, the researchers placed a water droplet containing on a water-repellent superhydrophobic surface and observed its oscillation in a magnetic field. The oscillation amplitude of the droplet decreases, as caused by the friction between droplet and surface. By modelling of the droplet motion, it was possible to extract information on the friction and kinetic .

For many years researchers have observed that easily slide from superhydrophobic surfaces, but so far no suitable methods could probe the friction accurately.

"It is remarkable that our method for measuring slipperiness becomes even more sensitive the lower the friction is," said Dr. Robin Ras of Aalto University. "Furthermore, unlike any previous method, we are able to discriminate between two sorts of friction, namely friction caused by viscous effects and contact angle hysteresis."

This video is not supported by your browser at this time.

Water-repellent have huge potential for self-cleaning applications, where surfaces do not get dirty. The first superhydrophobic surfaces are already on the market, such as self-cleaning clothing, and it is anticipated that they become more and more important in various technologies. Also superhydrophobic surfaces are appealing for microfluidics, where tiny amounts of liquid flow through channels for lab-on-a-chip applications.

"To develop superhydrophobic technologies further, it is important to know the friction droplets experience on these surfaces, and our method will contribute to that," explains Dr. Jaakko Timonen. "The compatibility to conventional meters will hopefully facilitate widespread use of our method."

This video is not supported by your browser at this time.

The article is titled "Free-decay and resonant methods for investigating the fundamental limit of superhydrophobicity". 

Explore further: Scientists examine the flow of liquid at the contact between randomly rough surfaces

More information: Nature Communications DOI: 10.1038/ncomms3398

Related Stories

Cicadas get a jump on cleaning (w/ Video)

April 29, 2013

As cicadas on the East Coast begin emerging from their 17-year slumber, a spritz of dew drops is all they need to keep their wings fresh and clean. Researchers at Duke University and James Cook University in Australia have ...

Physicists discover a new kind of friction in the nanoworld

May 15, 2013

Whether in vehicle transmissions, hip replacements, or tiny sensors for triggering airbags: The respective components must slide against each other with minimum friction to prevent loss of energy and material wear. Investigating ...

Explained: Hydrophobic and hydrophilic

July 16, 2013

Sometimes water spreads evenly when it hits a surface; sometimes it beads into tiny droplets. While people have noticed these differences since ancient times, a better understanding of these properties, and new ways of controlling ...

Researchers make droplets dance (w/ Video)

July 19, 2013

(Phys.org) —Researchers from Aalto University and Paris Tech have placed water droplets containing magnetic nanoparticles on strong water repellent surfaces and have made them align in various static and dynamic structures ...

Recommended for you

Short wavelength plasmons observed in nanotubes

July 28, 2015

The term "plasmons" might sound like something from the soon-to-be-released new Star Wars movie, but the effects of plasmons have been known about for centuries. Plasmons are collective oscillations of conduction electrons ...

'Expansion entropy': A new litmus test for chaos?

July 28, 2015

Can the flap of a butterfly's wings in Brazil set off a tornado in Texas? This intriguing hypothetical scenario, commonly called "the butterfly effect," has come to embody the popular conception of a chaotic system, in which ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

GaryB
not rated yet Sep 14, 2013
Clever.

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.