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. We propose using optical lift to power micromachines, transport microscopic particles in a liquid, or to improve the design of solar sails for interstellar space travel.
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