This article was posted on 02/04/2013

Researchers create mini tractor beam that pulls objects

Using light to attract objects is a much explored topic for almost a century. Perhaps you’ve tuned in to an episode of Star Trek in which characters use a “tractor beam” that could pull space ships and large objects toward it.

Back in November, Electronic Products told you about a team of researchers who made strides in this field when they used a laser beam to direct light in circles around a single dot, rather than a single beam.

Now, scientists from Scotland and Czech Republic, in association with the University of St. Andrews and the Institute of Scientific Instruments, have furthered progress in this area of study by creating a real-life miniature tractor beam by generating a special optical field that reverses radiation pressure of light.

A light beam is converted into a device that gathers micro-objects. (Image via University of St. Andrews)

Years of research have shown that normally, a radiation force occurs when matter and light attract causing an object to be pushed and carried away in a stream of photons. However, it has been discovered that there is a time when this force can reverse, when the matter is not pushed by the light but rather drawn in by it.

So the team tested a beam of light on polystyrene particles of different sizes and found that not only could the beam attract the particles, but they could also pull on certain particles.
The technique discovered by the researchers employs a “negative” force acting upon minuscule particles. The occurrence of the negative force is specific to the properties of the object such as size and composition, which allows for optical sorting of micro-objects in a simple and inexpensive device.

Researchers even found that objects held by the tractor beam force-field could re-arrange themselves in a way that actually made the beam stronger. Take a look at the self-arrangement video below, which shows that when the right configuration of particles forms, the tractor beam makes it stable and the whole structure moves against the beam.

In a study called “Optical Fractionation,” researchers discovered that this progress could have an impact on biomedical applications that would allow for sorting of cells, organelles, and macromolecules. Eventually, this could lead to better medical testing such as with blood samples which could result in better medical diagnostics.

Take a look at the video below to watch a demonstration of the sorting concept. You will see a mixture of particles of two different sizes. When the tractor beam is turned on, the larger particles are attracted (moving left) while the smaller particles are pushed to the right side.

Currently the research is only being done on a microscopic scale, so don’t expect to capture a spaceship any time soon.