Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Breaking the ice before it begins

15.11.2010
Nanostructured materials repel water droplets before they have a chance to freeze

Engineers from Harvard University have designed and demonstrated ice-free nanostructured materials that literally repel water droplets before they even have the chance to freeze.

The finding, reported online in ACS Nano on November 9th, could lead to a new way to keep airplane wings, buildings, powerlines, and even entire highways free of ice during the worst winter weather. Moreover, integrating anti-ice technology right into a material is more efficient and sustainable than conventional solutions like chemical sprays, salt, and heating.

A team led by Joanna Aizenberg, Amy Smith Berylson Professor of Materials Science at the Harvard School of Engineering and Applied Sciences (SEAS) and a Core Member of the Wyss Institute for Biologically Inspired Engineering at Harvard, focused on preventing rather than fighting ice buildup.

"We wanted to take a completely different tact and design materials that inherently prevent ice formation by repelling the water droplets," says Aizenberg. "From past studies, we also realized that the formation of ice is not a static event. The crucial approach was to investigate the entire dynamic process of how droplets impact and freeze on a supercooled surface."

For initial inspiration, the researchers turned to some elegant solutions seen in nature. For example, mosquitos can defog their eyes, and water striders can keep their legs dry thanks to an array of tiny bristles that repel droplets by reducing the surface area each one encounters.

"Freezing starts with droplets colliding with a surface," explains Aizenberg. "But very little is known about what happens when droplets hit surfaces at low temperatures."

To gain a detailed understanding of the process, the researchers watched high-speed videos of supercooled droplets hitting surfaces that were modeled after those found in nature. They saw that when a cold droplet hits the nanostructured surface, it first spreads out, but then the process runs in reverse: the droplet retracts to a spherical shape and bounces back off the surface before ever having a chance to freeze.

By contrast, on a smooth surface without the structured properties, a droplet remains spread out and eventually freezes.

"We fabricated surfaces with various geometries and feature sizes—bristles, blades, and interconnected patterns such as honeycombs and bricks—to test and understand parameters critical for optimization," says Lidiya Mishchenko, a graduate student in Aizenberg's lab and first author of the paper.

The use of such precisely engineered materials enabled the researchers to model the dynamic behavior of impacting droplets at an amazing level of detail, leading them to create a better design for ice-preventing materials.

Another important benefit of testing a wide variety of structures, Mishchenko adds, was that it allowed the team to optimize for pressure-stability. They discovered that the structures composed of interconnected patterns were ideally suited for stable, liquid-repelling surfaces that can withstand high-impact droplet collisions, such as those encountered in driving rain or by planes in flight.

The nanostructured materials prevent the formation of ice even down to temperatures as low as to degrees Celsius. Below that, due to the reduced contact area that prevents the droplets from fully wetting the surface, any ice that forms does not adhere well and is much easier to remove than the stubborn sheets that can form on flat surfaces.

"We see this approach as a radical and much needed shift in anti-ice technologies," says Aizenberg. "The concept of friction-free surfaces that deflect supercooled water droplets before ice nucleation can even occur is more than just a theory or a proof-of-principle experiments. We have begun to test this promising technology in real-world settings to provide a comprehensive framework for optimizing these robust ice-free surfaces for a wide range of applications, each of which may have a specific set of performance requirements."

In comparison with traditional ice prevention or removal methods like salting or heating, the nanostructured materials approach is efficient, non-toxic, and environmentally friendly. Further, when chemicals are used to de-ice a plane, for example, they can be washed away into the environment and their disposal must be carefully monitored. Similarly, salt on roads can lead to corrosion and run-off problems in local water sources.

The researchers anticipate that with their improved understanding of the ice forming process, a new type of coating integrated directly into a variety of materials could soon be developed and commercialized.

In addition to Aizenberg, who is also the Susan S. and Kenneth L. Wallach Professor at the Radcliffe Institute for Advanced Study and a Professor of Chemistry and Chemical Biology at Harvard, and Mishchenko, the co-authors of the paper included Benjamin Hatton and Vaibhav Bahadur, both at SEAS and Wyss, and Ashley Taylor and Tom Krupenkin, both at the University of Wisconsin-Madison.

The researchers acknowledge L. Stirling and A. Grinthal for their valuable contribution and funding from DARPA (Award Number HR0011-08-C-0114); the Wyss Institute for Biologically Inspired Engineering at Harvard University; and the U.S. Department of Homeland Security (DHS) Scholarship and Fellowship Program.

Michael Patrick Rutter | EurekAlert!
Further information:
http://www.harvard.edu/

More articles from Materials Sciences:

nachricht A new tool for discovering nanoporous materials
23.05.2017 | Ecole Polytechnique Fédérale de Lausanne

nachricht Did you know that packaging is becoming intelligent through flash systems?
23.05.2017 | Heraeus Noblelight GmbH

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>