Researchers at the University of Pennsylvania have managed to levitate objects using only light a prelude to what could be the equivalent of the magic carpet in children’s stories. That means that in the future, small planes powered by sunlight could fly in the mesosphere the layer of the Earth’s atmosphere that extends between 50 km and 80 km in altitude.
At that altitude, the atmosphere is very thin and contains only 0.1% of the total air mass. Under these conditions, airplanes and balloons cannot stay in flight but this new technology could allow very small airplanes to carry out research tasks of great scientific interest in the mesosphere.
Flying discs To achieve levitation by light, the researchers cut discs out of a transparent material called polyethylene terephthalate, also known as Mylar or Melinex. It is a type of plastic widely used in beverage and textile packaging. It is a polymer that belongs to the group of synthetic materials called polyesters.
The Mylar discs, 6 millimeters in diameter, were coated on their lower sides with carbon nanotubes, which have high electrical and thermal conductivity. The discs were placed inside a vacuum chamber made of acrylic material, along with eight light-emitting diodes (LEDs) that concentrated their energy on the two small plastic trays. When the right temperature was reached, the discs began to levitate inside the chamber at a pressure that mimicked that of the mesosphere.
THANKS TO NANOTUBES
Thanks to nanotubes As explained in the journal ScienceNews, carbon nanotubes are what allow the levitation of discs because they absorb light and heat the disc. Thanks to the characteristics of the nanotubes the air molecules obtain energy when they collide with the heated disk, bouncing at a higher speed. That extra energy translates into faster molecules that bounce off the underside of the Mylar disc faster than the top, thus causing it to levitate in small, powerful bursts.
Wired anticipates the possible applications of this technology it is the first instance of stable photophoretic (light-driven) flight which simulates how different plates would behave in the atmosphere.
AN EYE ON THE MESOSPHERE
An eye on the mesosphere The result indicates that a levitating disk, like a small magic carpet, could fly in the mesosphere carrying a charge the size of a sensor that would serve to study weather and climate from a new perspective. The mesosphere is traversed by shooting stars, cosmic rays of different colors, and energetic particles caused by solar storms that influence the ozone layer.
Having an observer in that thin layer of the Earth’s atmosphere is an old scientific aspiration that is now shaping up to be possible, although the technology that allows it still needs to overcome some challenges to become a reality. The levitating discs could be powered by sunlight or lasers and one day carries small instruments to measure conditions in the relatively unexplored mesosphere the researchers suggest.
Smart dust The photospheric levitation model obtained in this research allows us to calculate how these small flying objects will behave in different sizes and different atmospheric conditions. It has established, for example, that a 6-centimeter-diameter disk can carry a 10-milligram charge while levitating with this system, enough to support smart dust sensors. Smart dust is a wireless network of small sensors that can detect signals from light, temperature, vibrations, and other information from the environment.