Naturally occurring, optically driven, cellular rotor

We report the conversion of optical energy into mechanical energy by naturally occurring red blood cells (RBCs) placed in an optical trap. A trapped RBC undergoes folding due to the elastic nature of its cell membrane. On use of circularly polarized light in the trap, the folded RBCs rotate, indicating their birefringence. The cellular rotation speed depends on the size of the blood cells and on laser power. Rotating RBCs have implications for naturally occurring, optically driven, rotary micromachines. (C) 2004 American Institute of Physics.