Caltech Scientists Move Objects Using Only Light

What if a spacecraft could travel through our solar system powered and accelerated using only light? That’s the goal of new research coming out of Caltech. 

Researchers there have developed a way to levitate and propel objects using only light, by adding specific nanoscale patterning to their surface. Scientists have the ability to move and manipulate tiny objects with the use of ‘optical tweezers.’

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The tweezers move objects via the radiative pressure from a sharply focused beam of laser light. However, this impressive tool can only move small very small objects a very limited distance. 

Ognjen Ilic, a postdoctoral scholar, and the study's first author gives an analogy: "One can levitate a ping pong ball using a steady stream of air from a hairdryer. But it wouldn't work if the ping pong ball were too big, or if it were too far away from the hair dryer, and so on."

Precise pattern leads to levitation

New research is now working in ways to move objects in a range of sizes and shapes using only beams of light. The trick is to create very specific patterns on the object's surface. 

These nanoscale patterns interact with the light so that the object keeps ‘righting’ itself if disturbed so that it creates a restoring torque to keep it buoyant by the light.

This means that an object can keep itself stable and not rely on highly focused beams. The patterns could even mean the light source is millions of miles away from the object.

Light-based propulsion a possibility

"We have come up with a method that could levitate macroscopic objects," says Atwater, who is also the director of the Joint Center for Artificial Photosynthesis. 

"There is an audaciously interesting application to use this technique as a means for propulsion of a new generation of spacecraft. We're a long way from actually doing that, but we are in the process of testing out the principles."

This research provides the conceptual theory that a spacecraft could be ‘powered’ through space from Earth-based laser light. The craft would not need to carry fuel allowing it to go relativistic speeds and possibly travel to other stars.

Possible application for manufacturing

Spacecraft that don't need fuel for propulsion would be a huge boost for the future of space-colonies.  The fuelless craft could be used for intra-planet travel or as reconnaissance vehicles.   

The technologies developers are also exploring ways which it could be used to enable rapid manufacturing of ever-smaller objects, like circuit boards. The research has been published in the March 18 issue of the journal Nature Photonics.