Tractor Beams: From Fictional to Physical Reality

Category Science

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Tractor beams are a once fictional technology which have now become a reality thanks to recent advances in physics and technology. They use laser or sound waves to manipulate particles, molecules, or larger objects from a distance and have potential applications in fields like healthcare and precision manufacturing. The physics behind how they work involves momentum transfer between the tractor beam and the object it is manipulating.

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What is a tractor beam? .

Tractor beams use laser or sound waves to manipulate particles, molecules, or larger objects from a distance. The term "tractor beam" was first coined by science fiction author E. E. Smith in 1931, and since then, they have become a popular trope in science fiction. They are frequently shown in television and film as a beam of energy that can grasp and move items from a distance. For example, in Start Trek, starships can manipulate and move objects in space using tractor beams.

The tractor beam mentioned in Start Trek isn't technically a beam but instead an energy field.

But, recent advances in science and technology have moved the idea of tractor beams from science fiction to reality. In 2013, scientists created a tractor beam that could pull objects on a microscopic level. Since then, several studies have successfully created such small-scale tractor beams. For instance, in 2014, scientists created a reversible tractor beam that could transfer gold-coated hollow glass spheres against the power flow of a laser over tens of centimeters. In 2016, a study used tractor beams to move bacterial cells. More recently, in 2019, another study used tractor beams to assemble nanoscale materials in a process called "photonic nanosoldering." .

Using tractor beam technology, it is possible to pass microscopic objects from one side of a layer to another.

Although these developments might seem small, they have the potential to revolutionize many industries like healthcare, where they could be used to perform precise and non-invasive surgery.

So let's now take a look at the physics behind how they actually work.

--- The science behind tractor beams --- .

Tractor beams either use lasers or sound waves to move objects. This means there are two possible mechanisms by which a tractor beam can manipulate an object.

Tractor beams can produce a variety of forces such as pulling, pushing and manipulating forces.

The conceptual problem in explaining tractor beams is counter-intuitively linked with momentum. Photons carry momentum, which can be transferred to any object in the photon's path. This means the object will be 'pushed' away from the laser beam. This explains how an object can be moved away using tractor beams. But what about being attracted to the tractor beam? .

The foundational work came from Lee and colleagues in a paper published in 2010. In this study, they proposed using optical solenoid beams, which, unlike other light beams, had the unique property of exerting forces on illuminated objects in a direction opposite to the direction of light propagation, i.e., an attractive force.Thanks to scientists, tractor beams are now a reality. Source: Abel M'Vada via GIPHY .

The first successful demonstration of a real-world tractor beam system was conducted in 2011 at the University of St. Andrews in Scotland.

This research was further confirmed in 2011 by Chen and colleagues in a paper published in Nature Photonics. They mathematically established the condition for the existence of an optical pulling force, which causes objects to be moved toward the beam. Chen and his team showed that the attractive force could move an object as large as a ping-pong ball.The strength of this attractive force depends on the total amount of energy contained in the laser beam. Thus, the more intense the laser beam, the stronger the force and power of the tractor beam.

Tractor beams are capable of transporting objects with a range of materials including liquids and suspended particles.

In addition, research into tractor beams can help scientists better understand physics on the nanoscale. This is key to unlocking even more potential applications for this exciting technology.

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