New coating turns ordinary glass into superglass

The SLIPS coating makes glass so slippery

A droplet of octane, an ingredient of gasoline, rolls off a watch glass in just one second




Super-slippery SLIPS coating now transparent and more durable

By Randall Marsh August 8, 2013
Joanna Aizenberg, Ph.D. and her team at the Wyss Institute for Biologically Inspired Engineering at Harvard University have improved upon the Slippery Liquid-Infused Porous Surfaces (SLIPS) technology they developed back in 2012. The ultra smooth surface, which the team claims is the slipperiest known synthetic surface, has now been made transparent and more durable, giving it the potential to make the issues glass has with sticky liquids, frost and ice formation, and bacterial biofilms a thing of the past.

The develop the ultraslippery coating a glass honeycomb-like structure with craters is cre...The tightly packed cells of the honeycomb-like structure make the SLIPS coating highly dur...The incredibly slippery coating repels liquids with incredible easeThe coating was bio-inspired by the carnivorous pitcher plantView all
Instead of lotus leaves, which have been the inspiration for numerous superhydrophobic surfaces, the SLIPS technology was bio-inspired by the carnivorous pitcher plant, which has incredibly slippery leaves that help it trap unsuspecting insects. By now making it transparent and longer-lasting, Aizenberg says they have extended SLIPS' potential to durable, scratch-resistant lenses for eyeglasses, self-cleaning windows, improved solar panels, and new medical diagnostic devices.

To create the new coating, the researchers placed particles of Styrofoam (polystyrene) on a flat glass surface, and poured liquid glass on them until the particles were half submerged. Once the liquid glass solidified, the particles were burned away, leaving what the team describes as a "network of craters that resembles a honeycomb." The researchers then covered the craters with the same lubricant coating used in SLIPS.

The researchers found that the flat, glass slides treated in this way were more rugged than flat surfaces simply treated with the SLIPS coating, but they remained equally slippery, repelling everything from wine, olive oil, ketchup and octane. They also repelled water, thereby preventing the build up of ice, giving it the potential to keep power lines, aircraft and cooling systems frost-free.

The researchers found that by reducing the diameter of the individual honeycomb cells to less than the wavelength of visible light, the coating became transparent, while retaining its robustness and slipperiness.

Now that this method has been proven, the researchers are working to improve it to make it easier to apply to curved glass and clear plastics.


http://www.gizmag.com/coating-makes-glass-tough-self-cleaning-slippery/28604/


ew coating turns ordinary glass into superglass

Date: Aug 2, 2013

Resilient, ultraslippery glass could lead to self-cleaning,
scratch-resistant windows, lenses, and solar panels

SLIPS super glass
Researchers create the ultraslippery coating by creating a glass honeycomb-like structure with craters (left), coating it with a Teflon-like chemical (purple) that binds to the honeycomb cells to form a stable liquid film. That film repels droplets of both water and oily liquids (right). Because it's a liquid, it flows, which helps the coating repair itself when damaged. Credit: Nicolas Vogel, Wyss Institute.
A new transparent, bioinspired coating makes ordinary glass tough, self-cleaning, and incredibly slippery, a team from the Wyss Institute for Biologically Inspired Engineering at Harvard University and Harvard School of Engineering and Applied Sciences (SEAS) reported online in the July 31 edition of Nature Communications.

The new coating could be used to create durable, scratch-resistant lenses for eyeglasses, self-cleaning windows, improved solar panels, and new medical diagnostic devices, said principal investigator Joanna Aizenberg, Ph.D., who is a Core Faculty Member at the Wyss Institute, Amy Smith Berylson Professor of Materials Science at SEAS, and a Professor of Chemistry and Chemical Biology.

The new coating builds on an award-winning technology that Aizenberg and her team pioneered called Slippery Liquid-Infused Porous Surfaces (SLIPS) -- the slipperiest synthetic surface known. The new coating is equally slippery, but more durable and fully transparent. Together these advances solve longstanding challenges in creating commercially useful materials that repel almost everything.

SLIPS was inspired by the slick strategy of the carnivorous pitcher plant, which lures insects onto the ultraslippery surface of its leaves, where they slide to their doom. SLIPS's thin layer of liquid lubricant allows liquids to flow easily over the surface, much as a thin layer of water in an ice rink helps an ice skater glide. Unlike earlier water-repelling materials, SLIPS repels oil and sticky liquids like honey, and it resists ice formation and bacterial biofilms as well.

SLIPS honeycomb
The tiny, tightly packed cells of the honeycomb-like structure, shown here in this electron micrograph, make the SLIPS coating highly durable. Credit: Nicolas Vogel, Wyss Institute.
Vogel, Aizenberg, and their colleagues sought to develop a coating that accomplishes this, but extends those capabilities further. The new SLIPS design surpasses existing coatings, which can be quite robust but not slippery or transparent, or, alternatively, transparent but not mechanically stable or repellent enough, Aizenberg said.

"The SLIPS-like coating is mechanically stable and has a long-lasting performance as a slippery surface because it’s composed of a sturdy honeycomb-like structure that holds lubricant in tiny, container-like pits," Vogel said.

To create this coating, the researchers corral a collection of tiny spherical particles of polystyrene, the main ingredient of Styrofoam, on a flat glass surface, like a collection of Ping-Pong balls. They pour liquid glass on them until the balls are more than half buried in glass. After the glass solidifies, they burn away the beads, leaving a network of craters that resembles a honeycomb. They then coat that honeycomb with the same liquid lubricant used in SLIPS.

Placing the SLIPS-like coating on glass slides confers unmatched mechanical robustness. Slides treated this way withstood damage and remained slippery after various treatments that can scratch and compromise ordinary glass surfaces and other popular liquid-repellent materials, including touching, peeling off a piece of tape, and wiping with a tissue.

The glass slides with the SLIPS coating also repelled a variety of liquids, just as SLIPS does, including water, octane, wine, olive oil, and ketchup. And, like SLIPS, the coating reduced the adhesion of ice to a glass slide by 99 percent. Keeping materials frost-free is important because adhered ice can take down power lines, decrease the energy efficiency of cooling systems, delay airplanes, and lead buildings to collapse.

By adjusting the width of the honeycomb cells to make them much smaller in diameter than the wavelength of visible light, the researchers made the coating completely transparent.

The researchers were also able to apply the SLIPS-like coating to glass slides in a pattern that confines liquid to specific areas -- an ability that’s important for various lab-on-a-chip applications and medical diagnostics.

"We set ourselves a challenging goal: to design a versatile coating that's as good as SLIPS but much easier to apply, transparent, and much tougher -- and that is what we managed," said Aizenberg.

The team is now honing its method to better coat curved pieces of glass as well as clear plastics such as Plexiglas, and to adapt the method for the rigors of manufacturing

SLIPS superglass
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"Joanna's new SLIPS coating reveals the power of following Nature's lead in developing new technologies," said Don Ingber, M.D., Ph.D., the Wyss Institute's Founding Director. "We are excited about the range of applications that could use this innovative coating." Ingber is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and Boston Children's Hospital, and Professor of Bioengineering at Harvard SEAS.

This work was funded by the Advanced Research Projects Agency-Energy (ARPA-E), the Air Force Office of Scientific Research, and the Wyss Institute. Nicolas Vogel received funding from the Leopoldina Fellowship program. In addition to Vogel and Aizenberg, the research team included: Rebecca A. Belisle, a former Wyss research assistant who is now a graduate student in Materials Science and Engineering at Stanford University; Benjamin Hatton, Ph.D., formerly a Technology Development fellow at the the Wyss Institute and a research appointee at SEAS who is now an assistant professor of materials science and engineering at the University of Toronto; and Tak-Sing Wong, Ph.D., a former postdoctoral research fellow at the Wyss Institute who is now an Assistant Professor of Mechanical and Nuclear Engineering at Penn State University.

http://wyss.harvard.edu/viewpressrelease/120