Intelligent Machines

Breaking the Law at the Nanoscale

When objects get very close, Planck’s law is violated.

Any time you see a piece of metal glowing red-hot, or turning yellow or white as it gets hotter, you’re watching Planck’s law in action. The century-­old principle, which describes how energy is radiated from an idealized nonreflective black object, applies to everything from a cast-iron frying pan to the surface of a star. But it turns out to have a loophole.

Close Up Professor Gang Chen with the vacuum chamber used in his research.

Planck’s law says that thermal emission of radiation at different wavelengths follows a precise pattern that varies according to the temperature of the object. When the German physicist Max Planck proposed the law, in 1900, he suspected that it wouldn’t apply when two objects were very close together. But it took until this year to prove his hunch, because keeping objects that close without letting them touch is a major challenge. Now MIT researchers have shown that heat transfer between objects a few nanometers apart can be three orders of magnitude greater than the law would predict.

Professor of power engineering Gang Chen and his team, graduate student Sheng Shen and Columbia University professor Arvind Narayanaswamy, PhD ‘07, described how they did it in a paper last summer in the journal Nano Letters. “If we use two parallel surfaces, it is very hard to push to nanometer scale without some parts touching each other,” Chen explains. Instead, they used a small, round glass bead next to a flat surface. The objects came closest to touching at just one point, making the separation much easier to maintain. The researchers were able to test separations as small as 10 nanometers.

The findings could lead to new kinds of photovoltaic devices for harnessing photons emitted by a heat source, making it possible to harvest energy from heat that would otherwise be wasted. They could also be useful in magnetic data-recording systems such as computer hard disks, where the space between the recording head and the disk surface is typically in the range of five to six nanometers. The head tends to heat up, and researchers have been looking for ways to manage the heat or even exploit it. For example, some recording materials need to be heated, usually with a laser beam, before their surfaces can be magnetized by the head. If researchers understand how heat transfer works at these distances, they might be able to design a way for the head to provide its own heating.

Further work is still needed to explore what happens at even smaller distances, Chen says, because the researchers don’t know exactly how much heat can be dissipated in closely spaced systems.

Get stories like this before anyone else with First Look.

Subscribe today
Already a Premium subscriber? Log in.

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

Insider Premium
$179.95/yr US PRICE

More from Intelligent Machines

Artificial intelligence and robots are transforming how we work and live.

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. Listen in 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 all of your free articles this month. This is your last free article this month. You've read of free articles this month. or  for unlimited online access.