not occur with spherical microparticles
under the same conditions.
Why did the researchers use semicylinders instead of the more familiar
airplane-wing shape? “Rods having a
semicircular cross section are an approximation of a simple airfoil, and moreover,
they are easy to fabricate,” Swartzlander
said. “As with airplane wings, the optimal shape may depend on the application.” Optimization remains one of the
next directions for the research.
The particles in the Rochester demonstration experienced piconewton-scale
forces, which Swartzlander compared
to the force that bacteria use to propel
themselves through water. That may
sound tiny, but a carefully fabricated
array of billions of well-optimized
“lightfoils” could create several newtons
of force, enough to steer a small payload
Grover Swartzlander Grover Swartzlander (left), Alan Raisanan, Tim Peterson and Alexandra Artusio-Glimpse
propelled by a light sail. The radiation
pressure that makes such a sail move
has been well known, but steering
mechanisms are still at the experimen-
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