Machine Design

Nanotech gets rid of the fog

A foggy mirror can slow your shaving, but a foggy windshield can ruin your whole day.

Two glass slides were placed in a freezer then brought out into humid air and positioned over a photo of a lotus. Slide one carries MIT's antifog coating. Slide two doesn't.

Neither might be a problem in the future if engineers at Massachusetts Institute of Technology have their way. They've invented a nonfogging coating made of alternating layers of silica nanoparticles and a polymer called polyallyamine. The silica in the coating strongly attracts water, forcing water droplets to make smaller contact angles with the surface. This flattens the droplets, letting them merge into a transparent sheet rather than letting them form individual light-scattering spheres.

The same coatings can be engineered for better antireflective characteristics, reducing glare, and maximizing the amount of light passing through. This would be useful for greenhouses and solar panels. Currently, the coatings are more durable on glass than plastic, but the MIT team is optimizing the coatings for all surfaces.

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