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teamof researchers fromthe University of Bristol has shown it is possible to create a simplified tractor beamusing readily available parts at a total cost of less than £70. Tractor beams are
mysterious rays that can grab and attract objects. The concept has been shown in science-fiction movies such as Star Trek or StarWars and scientists have developed the theory using lasers. More realistically perhaps, tractor beams using
sound waves open up lots of applications for contactless handling. For instance, samples of blood could be levitated for visual inspection without any obstruction; chemical compounds could bemerged without being contaminated and kidney stones could be removed fromthe body without the need for incisions. And recently, sound was used to create a working tractor beamthat canmove heavier objectsmade of differentmaterials and that operates both in air and water without damaging the trapped objects. Now, researchers fromthe Department of
Mechanical Engineering at the University of Bristol have shown that it is possible to build a simplified tractor beamusing only one electrical signal and a passive wavemodulator. The passive wavemodulator is a type of acoustic
lens that can alter the transmitted or reflected waves. The research team’s passive wavemodulator
56 /// Environmental Engineering /// April 2017
Science fiction into science fact: the University of Bristol’s simplified tractor beamexerting its force on a small red ball
can bemade in various different ways, including a collection of tubes with different lengths or a carefully contoured surface. In both cases it can be 3D printed using an off–the-shelf printer. AsierMarzo, Research Assistant and the lead
author, said: “The technique can generate an acoustic tractor beamusing only a single electrical signal, this will reduce the cost and complexity of tractor beamsmaking themamore affordable technology formanipulating and analysing levitated samples.With our new research, now everyone can have an acoustic tractor beam.” EE
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