. 24/7 Space News .
TECH SPACE
New surfaces delay ice formation
by Staff Writers
Washington DC (SPX) Oct 08, 2015


This video shows droplets coalescing and growing on a biphilic surface. Over time the drops are pinned and pulled into the hydrophilic spots. The video is sped up approximately 7.5 times. Image courtesy Amy Betz/Kansas State University. Watch a video on the research here.

If you've ever waited on an airport runway for your plane to be de-iced, had to remove all your food so the freezer could defrost, or arrived late to work because you had to scrape the sheet of ice off your car windshield, you know that ice can cause major headaches.

"People intuitively know that frost can be bad," said Amy Betz, a professor in mechanical engineering at Kansas State University. Betz and her colleagues have created a surface that can significantly delay frost formation, even at temperatures of down to 6 degrees Celsius below freezing. The surface is biphilic, meaning it repels water in some areas and attracts it in others. The researchers describe their results in a paper in the journal Applied Physics Letters, from AIP Publishing.

Previous research by other groups has focused mainly on the frost-preventing properties of superhydrophobic (ultra water-repelling) surfaces. In general, the surfaces work by repelling water droplets before they have time to freeze. There is little research, however, on surfaces that mix hydrophobic and hydrophilic areas.

Betz had experience working with such biphilic surfaces for boiling experiments - in 2012 she and her colleagues found that superhydrophilic surfaces with superhydrophobic hexaganol spots resulted in the most efficient transfer of heat during boiling, compared to surfaces with uniform wettability. She wondered how similar "split personality" surfaces would affect ice formation.

Betz, along with fellow Kansas State University mechanical engineering professor Melanie Derby, and students Alexander Van Dyke and Diane Collard, created three different biphilic surface patterns. Each surface consisted of hydrophilic circles on a hydrophobic background. For two of the surfaces, the circles were 200 micrometers across, and either arranged in an even grid, like the dots on the 4-side of dice, or staggered, like the dots on the 5-side of dice.

The third surface consisted of smaller, 25 micrometer-sized circles in an even grid. The researchers also made a purely hydrophobic surface and a purely hydrophilic surface.

The team then tested the surfaces by placing them in a chamber at a range of set temperatures and humidities and waiting for three hours to see if frost formed. Ice crystals appeared at the warmest temperatures for the hydrophilic surface - at about 1-2 degrees Celsius below freezing.

The hydrophobic surface decreased the temperature required for freezing in the three-hour time frame by about an additional 1 degree Celsius. But the biphilic surfaces had the most success. At 60 percent relative humidity, all three biphilic surfaces required temperatures around 6 degrees below freezing before ice would form in the three-hour window.

The researchers attribute the frost-busting properties to the unusual condensation and coalescence dynamics on the biphilic surfaces. Small droplets about 5 micrometers in diameter initially formed on both the hydrophobic and hydrophilic areas, Betz said, but as the droplets grew, they merged with other droplets, and became confined to the hydrophilic spots.

Each time a droplet merged with another droplet it released energy held by surface tension, because the surface area of the new droplet was smaller than the combined surface area of the two droplets prior to merging. The new droplet was also larger, which increased the energy removal needed to freeze it. Both factors delayed the freezing of the droplets, the researchers said.

The researchers believe they can change the biphilic pattern to take maximum advantage of the frost-delay that coalescing droplets provide. "We are currently working on a star shape that should maximize coalescence," Betz said. The sizes and shapes of the surfaces could also be tuned to resist frost best in particular temperature and humidity environments.

The researchers made the surfaces from silicon wafers and a thin coating of a hydrophobic chemical commonly used in the semiconductor industry. The surfaces were strong enough to withstand hundreds of hours of testing over two years, but Betz said that more robust materials would likely be used for commercial applications of frost resistant surfaces. She said airplane wings are one obvious application, but there are many others, including in refrigerators, air conditioners, and air-cooled condensers in power plants.

"It's hot and humid in Kansas and the summer I first moved here a lot of people were having problems with their air conditioning units freezing up," Betz said, referring to a common problem where insufficient airflow or low refrigerant levels cause ice to build up on the AC units, forcing homeowners to turn the units off to defrost them. "Maybe a biphilic surface could help."

The article, "Droplet coalescence and freezing on hydrophilic, hydrophobic, and biphilic surfaces," is authored by Alexander S. Van Dyke, Diane Collard, Melanie M. Derby and Amy Rachel Betz. It will be published in the journal Applied Physics Letters on October 6, 2015 (DOI: 10.1063/1.4932050).


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only


.


Related Links
American Institute of Physics
Space Technology News - Applications and Research






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
TECH SPACE
New system allows heightened purity of a metal binding compound
Buffalo NY (SPX) Oct 06, 2015
A team of researchers from the State University of New York at Buffalo (University at Buffalo) have demonstrated a novel means of pre-purifying a natural product generated from a biosynthetic platform. The compound, termed yersiniabactin, has a unique ability to form strong complexes with metal ions, including iron and copper. As such, the compound has potential in a range of applications ... read more


TECH SPACE
Lunar Pox

Space startup confirms plans for robotic moon landings

Asteroids found to be the moon's main 'water supply'

Russian scientist hope to get rocket fuel, water, oxygen from Lunar ice

TECH SPACE
Lakes on Mars - SETI Editorial

NASA outlines obstacles to putting a human on Mars

ASU Mars images star in 'The Martian'

Mars colonisation still far off: Amitabh Ghosh

TECH SPACE
UTMB developing guidelines for commercial space travel

Dog smartphone and dancing humanoids on show at HK Fair

Aerojet completes major review of Orion subsystems

They're Loving It: Cheeseburgers Will Be Added to ISS Menu

TECH SPACE
Latest Mars film bespeaks potential of China-U.S. space cooperation

Exhibition on "father of Chinese rocketry" opens in U.S.

The First Meeting of the U.S.-China Space Dialogue

China's new carrier rocket succeeds in 1st trip

TECH SPACE
International Space Agencies Meet to Advance Space Exploration

Meet the International Docking Adapter

NASA extends Boeing contract for International Space Station

Russian launches cargo spaceship to the ISS

TECH SPACE
Both passengers for next Ariane 5 mission arrive in French Guiana

Arianespace signs ARSAT to launch a new satellite for Argentina

Ariane 5 orbits Sky Muster and ARSAT-2

A satellite launcher for the Middle East

TECH SPACE
Hubble Telescope Spots Mysterious Space Objects

Exoplanet Anniversary: From Zero to Thousands in 20 Years

Mysterious ripples found racing through planet-forming disc

The Most Stable Source of Light in the World

TECH SPACE
Using optical fiber to generate a two-micron laser

Dielectric film has refractive index close to air

Northrop Grumman upgrading G/ATOR radar system

Raytheon's AESA 360-degree radar moves toward production









The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.