Graphene sponge can be propelled by light

New Scientist : Another unexpected trait of graphene has been discovered—the ability to be propelled by photon impacts. Yongsheng Chen of Nankai University in Tianjin, China, and his colleagues were using lasers to cut sheets of crumpled graphene oxide, or graphene sponge, for another project and noticed that the graphene was being pushed around. That behavior was unexpected because lasers have never propelled anything larger than individual atoms. Chen’s team then put pieces of graphene sponge in a vacuum and shined different wavelengths and intensities of light on them and measured the distance the sponge moved. Even more unusual, the movement was greater than what could be expected from simple momentum transfer from the incoming photons. After further testing, the researchers were able to determine that the sponge builds up a charge from the photon impacts and then adds to its forward momentum by ejecting excess electrons.