Optical 'wrench' can move microparticles

The world's smallest wrench puts a new twist on laboratory manipulation by controlling single microscopic particles, U.S. researchers say. Using laser light's ability to gently push and pull microscopic particles, researchers have created the fiber-optic equivalent of the world's smallest wrench which can precisely twist and turn the tiniest of particles, from living cells and DNA to microscopic motors and dynamos used in biological and physical research, the Optical Society of American reported Monday. The laser-based technique is already used to perform optical "tweezing," which can move an object forward and backward along a straight line, but with the new "wrench" scientists for the first time will be able spin or twist microscale objects in any direction and along any axis without moving any of the optical components used, researchers at the University of Texas at Arlington said. "Optical tweezing is useful for biomedical and microfluidic research," lead researcher Samarendra Mohanty said. "But it lacks the control and versatility of our fiber optic spanner, especially when it comes to working deep inside." In the team's new device, the optical fibers use laser beams to first trap an object and then hold it in place. By slightly offsetting the optical fibers, the beams are able to impart a small twisting force, and depending on the positioning of the fibers it is possible to create rotation along any axis and in any direction, the researchers said.