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Scientists have created a new 'tractor beam' device that can move objects distances of up to several centimetres - about 100 times further than demonstrated in earlier experiments. The work has been published in Nature Photonics journal.
The concept of Tractor Beams, being able to move objects around remotely by use of a laser beam rather than having to physically interact up close with them, is an idea that has long been a staple of science fiction - The Enterprise in Star Trek has one, as does the Death Star in Star Wars.
Tractor beam experiments have previously used the momentum of photons, light particles, to provide force upon the objects. This idea worked but the process was difficult to control and takes a lot of energy to do. This latest device is different in that it harnesses the energy produced by a laser heating up the particles in the object and the surrounding air space. This process is more efficient, and the laser is reversible - so it can either be used to repel or attract the particles - providing great functionality.
The setup uses a hollow beam laser, which is bright around the edges and dark at the centre. The particles, gold-plated hollow glass spheres about a fifth of a millimetre in size, are localised at the dark centre of the beam. Energy from the laser is absorbed as it travels across the surfaces of the particles, creating "hotspots" - air particles colliding with these rapidly heat up and move quickly away from the surfaces, causing the particles to move in the opposite direction.
By changing the polarisation of the laser beam, the location of the hotspots could be changed, therefore changing the direction in which the particles moved. The particles were able to be moved up to 20cm, a distance hundreds of times their own size and significantly further than in previous tractor beam experiements.
The researchers envisage that because lasers retain their high beam quality over such long distances, the effect could be scaled up to move particles over much greater distances. Such a device could be used in future for practical applications such as studying atmospheric pollutants or retrieval of delicate particles for examination. We're still far from the technology being implemented in everyday use, the particles are light and the distances small, but progress is being made, and this is yet another sci-fi idea becoming reality that has the potential to be of great benefit to us.
Image Credits:
Star Trek Tractor Beam - The Institution of Engineers Australia, URL: https://www.engineersaustralia.org.au/portal/news/it%E2%80%99s-engineering-jim-not-we-know-it