Video of the week: How to build your own tractor beam

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This week's video comes from Bristol University where researchers have shown that a tractor beam can be built for under £70 with readily available parts.

Tractor beams seize and attract objects and scientists have been developing the theory using lasers. Sound has been used to create a working tractor beam that can move heavier objects made of different materials and operates in air or water without damaging the trapped objects.

In a paper published in Applied Physics Letters (APL), researchers from Bristol’s Department of Mechanical Engineering have shown that it is possible to build a simplified tractor beam using only one electrical signal and a passive wave modulator, which is a type of acoustic lens that can alter the transmitted or reflected waves.

According to the University, the passive wave modulator can be made in various different ways. In one example it’s a collection of tubes of differing lengths, and in another it’s a carefully contoured surface. In both cases, it can be 3D printed using an off–the-shelf printer. Using a single waveform a static tractor beam can be created. If two waveforms are used then up and down manipulation of objects can be achieved.

Asier Marzo, research assistant and the paper's lead author, said: “The technique can generate an acoustic tractor beam using only a single electrical signal, this will reduce the cost and complexity of tractor beams making them a more affordable technology for manipulating and analysing levitated samples. With our new research now everyone can have an acoustic tractor beam.”

Bruce Drinkwater, professor of ultrasonics in the University’s Department of Mechanical Engineering, added: “The process is so simple that we have released a YouTube video with instructions that show people how they can build their own acoustic tractor beam step-by-step with components that can be bought on the internet for less than £70.”

Previous work on tractor beams using sounds waves has opened applications for contactless handling. Samples of blood could be levitated for visual inspection without any obstruction; chemical compounds could be merged without being contaminated, and kidney stones could be removed from the body without the need for incisions.

However, to generate an acoustic tractor beam a phased array of more than 50 channels was required and each channel needs to be composed of a signal generator and an amplifier. These complex electronics have delayed the spread of acoustic tractor beams into biophysics or medical applications.