A cheap alternative to the lasers used in surgery has been devised using an energy source that is free and abundant - sunlight. The working prototype made by Israeli physicists concentrates sunlight down a fibre-optic cable to provide a tool for surgeons. Jeffrey Gordon and his colleagues at Ben-Gurion University in Israel hope it might one day replace the expensive surgical lasers used in operations such as the destruction of tumours in the liver. The light for the surgical "suntrap" is gathered by a parabolic mirrored dish, 20 centimetres across. This concentrates the light, which is then focused on to the tip of an optical fibre. The fibre can be up to 100 metres long. The device delivers less than a third of the light flux densities of surgical lasers, which have a typical output of 100 Watts per square-millimetre. "But in our clinical trial, we found that the optimal light density was just 3 W/mm2 for destroying liver cells," Gordon told New Scientist. "We were able to reach temperatures of 60 °C in the cells, which is enough to kill them." Full article here.