Hydrophobics Get Tough

New ceramics can take a beating and still shed water

Durable surfaces that can shed water could be useful in a variety of areas, including energy, water, transportation, construction, and medicine. The condensation of water is a crucial part of many industrial processes; most electric power plants and desalination plants, for example, have condensers.

water-shedding ceramics
These water-shedding ceramics may find uses in steam-based power plants, desalination plants, and other industrial applications.

Hydrophobic materials—which prevent water from spreading over a surface, instead causing it to form droplets that easily fall away—can make the condensation process more efficient. But most hydrophobic materials are made from thin polymer coatings that degrade when heated and are easily destroyed by wear. Now MIT researchers, including associate professor Kripa Varanasi and mechanical-­engineering postdoc Gisele Azimi, have come up with a new class of hydrophobic ceramics that can endure both extreme temperatures and rough treatment.

Ceramics are great at withstanding extreme temperatures, but they tend to attract water rather than repel it. To address this problem, the MIT team made ceramics out of the so-called rare-earth metals—elements whose unique electronic structure they thought might render the materials hydrophobic.

To test this hypothesis, the team used powder oxides of 13 of the 14 members of the rare-earth metal series (excluding one that is radioactive) and made pellets by compacting them and heating them nearly to their melting point in order to fuse them into solid, ceramic form—a process called sintering. “We thought they should all have similar properties for wetting, so we said, ‘Let’s do a systematic study of the whole series,’” says Varanasi, an associate professor of ocean utilization.

As predicted, all 13 displayed strong hydrophobic properties. “We showed, for the first time, that there are ceramics that are intrinsically hydrophobic,” Varanasi says.

The ceramic forms of rare-earth oxides could be used either as coatings on various substrates or in bulk form. Because their hydrophobicity is an intrinsic chemical property, Azimi says, it persists “even if they are damaged.”

Most previous research on hydrophobic materials and coatings has focused on surface textures and structure rather than on the materials’ chemical properties, Varanasi says. “No one has really addressed the key challenge of robust hydrophobic materials,” he says. “We expect these hydrophobic ceramics to have far-reaching technological impact.”

Become an MIT Technology Review Insider for in-depth analysis and unparalleled perspective.
Subscribe today

Uh oh–you've read all five of your free articles for this month.

Insider Premium

$179.95/yr US PRICE

Want more award-winning journalism? Subscribe and become an Insider.

  • Insider Premium {! insider.prices.premium !}*

    {! insider.display.menuOptionsLabel !}

    Our award winning magazine, unlimited access to our story archive, special discounts to MIT Technology Review Events, and exclusive content.

    See details+

    What's Included

    Bimonthly home delivery and unlimited 24/7 access to MIT Technology Review’s website.

    The Download. Our daily newsletter of what's important in technology and innovation.

    Access to the Magazine archive. Over 24,000 articles going back to 1899 at your fingertips.

    Special Discounts to select partner offerings

    Discount to MIT Technology Review events

    Ad-free web experience

    First Look. Exclusive early access to stories.

    Insider Conversations. Join in and ask questions as our editors talk to innovators from around the world.

  • Insider Plus {! insider.prices.plus !}* Best Value

    {! insider.display.menuOptionsLabel !}

    Everything included in Insider Basic, plus ad-free web experience, select discounts to partner offerings and MIT Technology Review events

    See details+

    What's Included

    Bimonthly home delivery and unlimited 24/7 access to MIT Technology Review’s website.

    The Download. Our daily newsletter of what's important in technology and innovation.

    Access to the Magazine archive. Over 24,000 articles going back to 1899 at your fingertips.

    Special Discounts to select partner offerings

    Discount to MIT Technology Review events

    Ad-free web experience

  • Insider Basic {! insider.prices.basic !}*

    {! insider.display.menuOptionsLabel !}

    Six issues of our award winning magazine and daily delivery of The Download, our newsletter of what’s important in technology and innovation.

    See details+

    What's Included

    Bimonthly home delivery and unlimited 24/7 access to MIT Technology Review’s website.

    The Download. Our daily newsletter of what's important in technology and innovation.

You've read of free articles this month.