TECHNOLOGY

Scientists have created a metal that is so extremely hydrophobic that water bounces on it as if it were repelled by a magic force field. Instead of using chemical coatings, the researchers used lasers to etch a nanostructure on the metal itself. (SPLOID)

Use our activity to better understand the properties of matter at the nanoscale.

Teachers, scroll down for a quick list of key resources in our Teachers’ Toolkit.

Discussion Ideas

• Watch these two terrific videos on superhydrophobic materials. The first one is from the good folks at the Children’s Museum of Houston, and it’s a great introduction. The second one, one from the good folks in the mechanical engineering labs at BYU, gives a little more background.
  
  
  
  • Based on these videos, how do you think the scientists at the University of Rochester created their superhydrophobic material?
    • The etching changed the texture of the surface of the metal, giving it “microgrooves,” dips, or “nanowhiskers” on an atomic or molecular level—learn more about the nanoscale here. (FYI: The metals the Rochester scientists used were platinum, titanium, and brass.) The water is much more attracted to itself than the uneven, corrugated surface of the etched metal, bouncing off the material in big, fat drops.

Read through our great activity, Properties of Matter: Macro to Nano Scale. Adapt the questions to reflect information in the article and video on superhydrophobic metal etched with nanostructures.

• What is a property of matter?
  • Properties of matter are characteristics that distinguish one sample of matter from another.

• What are some properties of matter?
  • Some properties of matter include color; luster (how shiny the matter is); malleability (how easily it can be shaped); its boiling or freezing point; taste and smell; or how well it conducts electricity.

• What property of matter is being altered by the nanostructures described in the SPLOID article or University of Rochester video?
  • The nanostructures are actually altering two properties of matter—how water-repellent the metal is and its texture.

• Water-repellence: Do a hands-on activity with everyday “waterproof” materials to see how well they repel water. What everyday materials did the scientists in the video use as their example? What other materials could you use?
  • The scientists in the video used a Teflon, or non-stick, cooking pan. (Why the capitalization? Teflon is a brand name coined by the brainiacs at DuPont. The material’s chemical name is polytetrafluoroethylene.) The Teflon-coated pan had to be tilted to about a 70-degree angle for water droplets to slowly slide off the surface. The nano-etched titanium did not need to be tilted to much of an angle at all, and water literally bounced off the surface—no drippy drops.
  • Besides Teflon cooking pans, everyday “waterproof” materials students might have access to may include the following. What is the angle to which they need to be tilted for water to drip off?
    • umbrellas, tents, clothes, and other “waterproof” fabric
    • freshly waxed car or other vehicle (or metal coated with the car wax)
    • watches
    • mobile phones
    • outdoor deck surface (or wood coated with the “weatherproof” substance)
    • boat surface (or plastic coated with the “waterproof” substance)
    • liquid containers, such as water bottles or milk cartons

• Texture: Do a hands-on activity with everyday materials to alter their texture. How did the scientists in the video alter the texture of the metal? How can you alter the texture of everyday materials?
  • The scientists in the video used a laser to etch nanostructures in the surface of the metal. This changed the surface on an atomic or molecular level!
  • Everyday materials that can change the surface texture of a substance might include:
    • sandpaper
    • polish
    • acid
    • wax
    • waterproof sprays

TEACHERS’ TOOLKIT

SPLOID: New amazing metal is so hydrophobic it makes water bounce like magic

Nat Geo: Properties of Matter: Macro to Nano Scale

(extra credit!) Journal of Applied Physics: Multifunctional surfaces produced by femtosecond laser pulses