No science fiction: researchers have developed metasurface tractor beams

By ARC Center of Excellence for Transformative Meta-Optical Systems July 21, 2024

High-efficiency triple helix solenoid beam generated by a dielectric metasurface

TMOS researchers have developed a metasurface solenoid beam that can attract particles to itself, which could revolutionise non-invasive medical procedures such as biopsies. The technology, which uses a thin layer of nanostructured silicon, offers a lightweight and portable alternative to the bulky equipment previously required for such beams. Credit: University of Melbourne

TMOS researchers have advanced the development of lightweight, portable tractor beams that could transform noninvasive medical procedures.

Researchers at TMOS, the ARC Centre of Excellence for Transformative Meta-Optical Systems, have made a significant first step in creating tractor beams powered by metasurfaces. These light beams, which can attract particles to them, are inspired by the fictional tractor beams seen in science fiction.

In research published in ACS PhotonicsThe University of Melbourne team describes their solenoid beam generated using a silicon metasurface. Previous solenoid beams have been created by 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 1/2000 of a millimetre thick. The team hopes that one day it could be used to perform biopsies non-invasively, unlike current methods such as forceps that cause trauma to surrounding tissue.

Light beams tend to exert a pushing force, pushing particles away from the light source. Solenoid beams have been shown to attract particles toward the light source. Consider how a drill works, pulling wood chips toward the drill bit. Solenoid beams work in a similar way.

Benefits of the new solenoid harness

This particular solenoid beam has several advantages over previously generated solenoid beams, in that the input beam requirements are more flexible than with previous beams, it does not require an SLM, and the size, weight, and power requirements are significantly lower than with previous systems.

The metasurface was created by mapping the phase hologram 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 to a solenoid beam and deviates from the unconverted beam, allowing the researchers to work with it without obstruction. They were able to characterize the beam at a distance of 21 centimeters.

Maryam Setareh, lead researcher, said: “The compact size and high efficiency of this device could lead to innovative applications in the future. The ability to extract particles using a metasurface could impact the field of biopsy by potentially reducing pain through less invasive methods.”

Setareh says: “We are excited to study the performance of our device in particle manipulation, which could provide valuable insights.”

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

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

Reference: “High-efficiency triple helix solenoid beam generated by a dielectric metasurface” by Maryam Setareh, Robert De Gille, Jasper Cadusch, Dandan Wen, Sejeong Kim, and Kenneth B. Crozier, July 17, 2024, ACS Photonics.

DOI: 10.1021/acsphotonics.4c00874