We demonstrate controlled rotation of optically trapped objects in a spiral
interference pattern. This pattern is generated by interfering an annular
shaped laser beam with a reference beam. Objects are trapped in the spiral
arms of the pattern. Changing the optical path length causes this pattern,
and thus the trapped objects, to rotate. Structures of silica microspheres,
microscopic glass rods, and chromosomes are set into rotation at rates in
excess of 5 hertz. This technique does not depend on intrinsic properties o
f the trapped particle and thus offers important applications in optical an
d biological micromachines.