Researchers develop tractor beams with metal surface

TMOS researchers have developed lightweight, portable tractor beams that could transform non-invasive medical procedures.

Researchers at TMOS, the ARC Center of Excellence for Transformative Optical Systems, have made significant first progress in creating doped tractor beams on metasurfaces. These light beams, which can attract particles towards them, are inspired by the fictional tractor beams seen in science fiction.

In a study published in ACS OpticsThe University of Melbourne team describes a solenoid beam created using a silicon metasurface. Previous solenoid beams have been created using bulky special light modulators (SLMs), but the size and weight of these systems prevent their use in portable devices. The metasurface is a layer of nanostructured silicon only about 1/2000th of a millimetre thick. The team hopes it could one day be used to perform biopsies non-invasively, unlike current methods such as forceps that traumatise surrounding tissue.

Light rays tend to exert a buoyant force, pushing particles away from the light source. Solenoid belts have been shown to pull particles toward the light source. Consider the operation of a drill that pulls wood chips toward the drill bit. Solenoid belts work in the same way.

Advantages of harnessing the new solenoid

This coil pack has several advantages over previously constructed coil packs, as the input beam requirements are more flexible than previous packs, it does not require SLM and the size, weight and power requirements are much lower than previous systems.

The metasurface was created by 3D mapping the phase of the desired beam. This was used to create a pattern. The metasurface was then fabricated from silicon using electron beam lithography and reactive ion etching. When the input beam, in this case a Gaussian beam, filters through the metasurface, most of it (about 76%) is converted into a solenoid beam and deflected from the unconverted beam, allowing the researchers to work with it unobstructed. They were able to characterize the beam at a distance of 21 cm.

“The small size and high efficiency of this device could lead to innovative applications in the future,” said Maryam Setara, lead researcher. “The ability to extract molecules using a superficial surface could impact the field of biopsy by reducing pain through less invasive methods.”

“We are excited to study the performance of our devices in handling particles, which could provide valuable insights,” says Stareh.

“The next step in this research will be to experimentally demonstrate the beam’s ability to attract particles, and we look forward to sharing these results when they become available,” said lead researcher Ken Crozier.

“This work opens up new possibilities for using light to exert forces on small objects,” Crozier says.