A new Star Trek-like tractor-beam technology is advancing optical tweezer technology beyond of the realm of science fiction, according to findings detailed in a new study.
Optical tweezers manipulate atoms and nanoparticles using laser beams. These beams act like tweezers but use focused light instead of steel to hold small objects. By controlling the beam, operators can move and manipulate tiny particles without physical contact. The technology holds promise for nanoscale work, but many obstacles have held it back.
A Tractor Beam for DNA
The devices aid biologists in investigating DNA, classifying cells, and peering into how diseases operate. While they may be designed to work on tiny particles, traditional optical tweezers are anything but. They generally require an extensive microscope installation and other bulky apparatus for forming and controlling light. By moving toward a chip-based design produced using a fabrication process known as silicon photonics, optical tweezers eliminate these problems and become more mass-producible and accessible.
“With silicon photonics, we can integrate this large, typically lab-scale system onto a chip. This presents a great solution for biologists since it provides optical trapping and tweezing functionality without the overhead of a complicated bulk-optical setup,” study co-author Jelena Notaros said.
Mini Star-Trek-Like Tractor Beams
Moving towards a chip-based device’s much smaller form factor solves these issues but creates some new ones. Previous attempts to develop such a device suffered due to their limited reach. Their weak beams could only hold cells that were extremely close or right on the chip. The problem with that is that the chip can become contaminated with the cells, while the cells can be damaged or contaminated by the chip.
The innovation that moves a chip-based solution ahead is an exponentially increased range. Taking cues from other long-range lasers like lidar, the team rethought chip-based optical tweezers from the ground up. Generally, lidar arrays aren’t designed to create intense, tight-focused beams. In their research, the team worked to develop wave patterns for each antenna that would combine the intensity needed for an optical tweezer with increased distance inspired by lidar into an optical phased array.
Testing a Tractor Beam
They fabricated the tiny antennas required using traditional semiconductor techniques. With the finished product in hand, they began testing in a real-world environment using small polystyrene spheres. Once they could successfully manipulate inorganic objects, they moved on to successfully trapping and moving cancer cells with the device.
This new silicon photonics chip can interact with particles separated from it by several millimeters. This provides enough distance to work on the samples while they remain in a sterile glass-enclosed environment. By changing the wavelength of the signal fed into the chip, they could successfully steer the beam with microscale precision.
“No one had created silicon-photonics-based optical tweezers capable of trapping microparticles over a millimeter-scale distance before. This is an improvement of several orders of magnitude higher than prior demonstrations,” said Notaros.
While the new design can be mass-produced as-is, the team hopes to improve it further. They emphasize creating more complex versions of the chip to allow more dynamic particle manipulation. Examples of future improvements they envision include an adjustable focal height for the beam and using multiple trap sites.
The paper “Optical tweezing of microparticles and cells using silicon-photonics-based optical phased arrays” was published in Nature Communications on October 3, 2024.
Ryan Whalen covers science and technology for The Debrief. He holds a BA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.