Scientists Built a ‘Tractor Beam’ That Could Expand Frontiers in Physics
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Microscope “tractor beams,” known to scientists as optical tweezers, come in either bulky, expensive setups or smaller, chip-sized devices.
However, this second type of devices has one major downside—they typically can’t manipulate cells far away from the surfaces of their chips, which can damage the samples being studied.
MIT researchers believed they’ve solved this problem by creating a new phase pattern for the microscale antennae on the chip, making it possible to “tractor beam” particles more than a millimeter from the chip’s surface (roughly 100 times further than what was previously possible).
“Engage the tractor beam” is a well-known sci-fi turn of phrase, but the idea of this kind of energy manipulation is more real than you might think. In recent years, scientists have developed tractor beam-like tech with the hopes of cleaning up some space junk or moving other kinds of macro-sized objects around.
And while images of the U.S.S. Enterprise or the Death Star bringing some rogue spaceship to heel come to mind, tractor beams in the here and now are most applicable in the microscopic world, where they’re more commonly known as optical tweezers. At its most basic, this technique uses light to manipulate incredibly small objects—down to the size of a single atom. Despite this extremely small use case, most of these devices are bulky, specialized setups. But now, scientists at MIT have successfully created a tractor beam device that fits in the palm of your hand and can manipulate objects much further than previous chip-based forebears. The researchers detailed their work last month in the journal Nature Communications.
Unlike their bulky counterparts, chip-based tweezers are compact, mass manufacturable, and more broadly accessible. But they come with a pretty big downside—the distance of their “tractor beams” don’t extend very far beyond the surfaces of the chips themselves. This can sometimes damage the chips, as well as the cells that are being studied. However, the MIT team thinks they’ve overcome this limitation by using an integrated optical phase array that can manipulate cells over more than 100 times more distance than was previously possible.
“This work opens up new possibilities for chip-based optical tweezers by enabling trapping and tweezing of cells at much larger distances than previously demonstrated,” MIT’s Jelena Notaros, senior author of the study, said in a press statement. She also called the breakthrough “an improvement of several orders of magnitude” compared to previous attempts. “It’s exciting to think about the different applications that could be enabled by this technology.”
Optical traps and tweezers work by capturing and manipulating tiny particles in focused beams of light. Then, researchers can steer the beams any which way they choose. However, biological specimens are typically sterile (via a glass coverslip that’s some 150 microns thick), so increasing the control distance beyond a millimeter is really valuable. And because of the system’s cheap cost (compared to expensive microscope set-ups), it could also give more labs access to this useful research tool.
“With silicon photonics, we can take this large, typically lab-scale system and integrate it onto a chip.” Notaros said in a press statement. “This presents a great solution for biologists, since it provides them with optical trapping and tweezing functionality without the overhead of a complicated bulk-optical setup.”
To create the chip, researchers used an integrated optical phase array, which contains microscale antennae that are individually capable of steering the beam of light emitted by the chip. MIT’s breakthrough developed a novel phase pattern for each antenna so that it could perform optical trapping and tweezing far from the chip’s surface.
So, while these microscope tractor beams may not be thwarting the evil plans of some galactic ne’er-do-well any time soon, they’re exploring an exciting frontier of discovery all their own.
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