Scientists from the Rochester Institute of Technology have recently demonstrated that micrometers-long, airplane-wing-shaped rods can be lifted by a beam of laser light. This research has the potential to upgrade solar sail technology and power microscopic machines.
Scientists are aware that light can be used to simply propel matter, but this is the first time light has been used to provide lift. The scientists used the light of a laser to lift tiny, half-cylindrical plastic objects as if they were airplanes taking off. They put these rods in water and hit them with a 130 milliwatts of light. When hit with light, these rods moved upward and over at a 60 degree angle. According to researcher Dr. Grover Swatzlander, "your stomach would be in your feet" if an airplane took off at this angle.
How do the lightfoils in these experiments differ from the airfoils on an airplane? The aerodynamic lift of an airfoil is caused by the higher pressure of the air flowing under the wing, whereas the transparent lightfoil experiences greater radiation pressure in a direction perpendicular to its light source, which in turn creates lift. These findings could improve the mobility of future solar sails and could pioneer microscopic machines.
Here's what the RIT team had this to say about their findings, which were published December 5 in the journal Nature Photonics:
We have predicted and observed an optical analogue of aerodynamic lift, in which a cambered refractive object with differently shaped top and bottom surfaces experiences a transverse lift force when placed in a uniform stream of light. A semi-cylindrical rod is found to automatically torque into a stable angle of attack, and then exhibit uniform motion. We have experimentally verified this using a micrometer-scale ‘lightfoil' which was fabricated using photolithographic techniques, immersed in water and illuminated with milliwatt-scale laser light. Unlike optical tweezers, an intensity gradient is not required to achieve a transverse force. Many rods may therefore be lifted simultaneously in a single quasi-uniform beam of light.
And here's video of the lightfoil being lifted:
[Spotted on Physorg]