A team of Chinese physicists has developed a new variety of light-based propulsion system with the ability to harness much greater forces than a conventional solar sail. The key, according to the Nankai University-based group, is in swapping out the mirrored sail—which captures photonic energy as radiation pressure in much the same way a regular air-sail captures wind energy—for a pure-black graphene sponge. Rather than reflect off of the sail, light is absorbed by the sponge, which converts that energy into propulsion.

The group's work is published this week in Nature Photonics.

Using light and lasers to move stuff around isn't exactly new. Scientists have trapped, moved, levitated, and pulled all manner of micro and nanoscale objects, including graphene, but also cells, viruses, single molecules, and atoms. Really small stuff.

In one particular form, the concept is known as optical tweezers, which are IRL, not uncommon scientific instruments. The dream, however, is to scale light-based manipulation up to the world of the macroscopic, which is our (visible) world.

"If these optical operations were to be achieved with large objects on a macroscopic spatial scale, significant applications such as the long-sought direct optical manipulation of macroscale objects—including the proposed solar sail and space transportation via laser or beam-powered propulsion—could be realized," the Chinese group, led by civil and environmental engineering professor Yongsheng Chen, writes.

Enter our graphene sponge, which offers just that macroscale manipulation.

The general idea is this. Graphene can absorb light like few if any other known materials, making it indeed a perfect or close-to-perfect photonic "sponge." The result, referred to as "efficient light-induced ejected electron emission" in the paper, is that the electrons within the material get extra excited or energetic and some of them pop right back out of the material. As the electrons bounce away from the graphene, there is a backwards push against it, just as you'd expect from Newtonian mechanics. Every action has a corresponding reaction and, here, that reaction is motion or a transference of momentum. The sponge moves.