AMSTERDAM, The Netherlands, June 18 -- Chemists from Utrecht University and Philips Research have used an electrical field to regulate the flow of light through a liquid. The researchers developed a liquid containing metal nano-rods ; the tiny metal rods move at random in suspension and can change the liquid's ability to screen out the sun.The rods have a diameter that can be altered from 12 to 22 nanometers and an adjustable length of between 40 and 730 nanometers. They absorb light of a certain color, and the electrons resonate with the light over the length of the rod. The color of the light absorbed depends on the length of the rod. The scientists used an electrical field to alter the orientation of the rods, and found that if all rods are oriented in the same direction, the liquid hardly absorbs any light at all. Possible uses for this research include electrical sunscreens in such applications as car windows.