Columbia University

Technology Ventures

Biomimetic passive cooling and heating system

Technology #cu15297

Although passive cooling systems are an attractive way to reduce the need for energy-intensive air conditioning, most of these systems can only cool passively at night when they are not subject to solar radiation. This technology is a surface coating inspired by the hairs of the African silver ant that can reflect visible and near-infrared (near-IR) radiation and increase mid-infrared (mid-IR) emission from an object. It can also be modified to allow for passive heating by increasing absorption of radiation and reducing emission. This coating can potentially be used as a passive cooling or heating system by applying it to surfaces such as the roofs and walls of buildings and cars, the exteriors of space shuttles, satellites, industrial equipment, and textiles.

Tunable surface coating increases reflection and emission of IR radiation

The African silver ant has hairs that can reflect up to 60% of visible and near-IR radiation, depending on the angle of incidence. The hairs also increase the emission of mid-IR radiation from the ant by up to 15%. This technology mimics the function of the ant’s hairs using inexpensive inorganic materials such as silicon dioxide, silicon nitride, and titanium dioxide, as well as polymers and nanoparticles, to create hair-like structures on a surface coating. The exact materials and shapes (e.g. triangular, trapezoidal, pyramidal) of the coating can be fine-tuned according to the exact wavelength of the radiation that will be reflected, emitted or absorbed. This technology can also be utilized in applications beyond passive cooling and heating, such as reducing the IR signature of military aircraft and vehicles.

Lead Inventor:

Nanfang Yu, Ph.D.


  • Passive cooling of buildings, cars, space shuttles, satellites, solar panels and industrial equipment
  • Self-cooling textiles for athletic wear, military uniforms, and more
  • Reducing IR signature of airplanes, armored vehicles, and military personnel
  • Increasing solar panel absorption


  • The coating’s structure and materials can be tuned for either cooling or heating
  • Uses inexpensive, readily available materials such as silicon, titanium and aluminum oxides.
  • Can be applied to flexible surfaces for roll-to-roll processing

Patent Information:

Patent Pending (WO/2016/205717)

Tech Ventures Reference: IR CU15297

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