Tractor beams are a well-known concept in science fiction. Theserays of light are often shown pulling objects towards an observer,seemingly violating the laws of physics, and of course, such beamshave yet to be realised in the real world. Haifeng Wang at theA*STAR Data Storage Institute and co-workers have now demonstratedhow a tractor beam can in fact be realized on a small scale."Our work demonstrates a tractor beam based only on a singlelaser to pull or push an object of interest toward the lightsource," says Wang. Based on pioneering work by Albert Einstein and Max Planck morethan a hundred years ago, it is known that light carries momentumthat pushes objects away. In addition, the intensity that variesacross a laser beam can be used to push objects sideways, and forexample can be used to move cells in biotechnology applications.Pulling an object towards an observer, however, has so far provento be elusive. In 2011, researchers theoretically demonstrated amechanism where light movement can be controlled using two opposinglight beams -- though technically, this differs from the ideabehind a tractor beam. Wang and co-workers have now studied the properties of lasers witha particular type of distribution of light intensity across thebeam, or so-called Bessel beams. Usually, if a laser beam hits asmall particle in its path, the light is scattered backwards, whichin turn pushes the particle forward. What Wang and co-workers havenow shown theoretically for Bessel beams is that for particles thatare sufficiently small, the light scatters off the particle in aforward direction, meaning that the particle itself is pulledbackwards towards the observer. In other words, the behaviour ofthe particle is the direct opposite of the usual scenario. The sizeof the tractor beam force depends on parameters such as theelectrical and magnetic properties of the particles. Although the forces are not very large, such tractor beams do havereal applications, says Wang. "These beams are not very likelyto pull a human or a car, as this would require a huge laserintensity that may damage the object," says Wang."However, they could manipulate biological cells because theforce needed for these doesn't have to be large." Such applications are the driving force for future experimentaldemonstrations of such pulling effects. The technology could, forexample, be used to gauge the tensile strength of cells, whichwould be useful to investigate whether cells have been infected."For instance, the malaria-infected blood cell is more rigid,and this technology would be an easy-to-use tool to measurethis," adds Wang. The e-commerce company in China offers quality products such as Flexible Led Reading Light , China Led Keychain Lights, and more. For more , please visit Led Keychain Lights today!
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