A tiny metasurface “metajet” shows how light can be redirected to control motion in multiple directions, opening paths to steer light sails.
A light sail might be steerable after all, thanks to a microscopic device that can not only feel the push of light but also redirect the direction of that push.
Light sails are often described as giant, ultra-thin sheets that travel through space when photons bounce off them, transferring momentum.. The new work builds on that idea by showing how researchers can control not just the amount of momentum delivered by light. but the direction it drives—an advance that could help future spacecraft adjust their course over long distances.
The breakthrough comes from a team led by Kaushik Kudtarkar at Texas A&M University. who and colleagues created an extremely small device they call a “metajet.” Unlike approaches that rely mainly on reflection. the metajet uses refraction of light to generate motion that can occur in more than one direction at once.
At the heart of the device is a metasurface: a material made as an ultrathin sheet whose surface is patterned at the micro- or nanoscale to manipulate how light behaves.. In earlier uses, metasurfaces were typically designed to control light; here, the concept is flipped.. The researchers use the incoming light to control the metasurface’s response. steering how momentum is transferred from the light to the device.
A key design feature is a series of tiny pillars on the metasurface.. When the laser light hits this textured array. the pillars shape the light’s behavior so that the overall device experiences momentum in controlled directions.. In effect. changing the size and pattern of the pillars changes the “push” the light delivers. allowing the motion to be tuned through the metasurface geometry.
The device itself is extraordinarily small—about 0.01 millimetres across. To see whether the design truly produced controllable movement, the researchers placed the silicon metajet in water and shone a laser on it, then tracked its motion under a microscope.
Their measurements showed that the metajet did more than hover.. It levitated and also moved horizontally, reaching a maximum speed of about 0.07 millimetres per second.. The experiment directly demonstrated that the forces produced by the engineered light–material interaction can translate into measurable motion in different directions.
Once the researchers know how these forces act on the device. they argue the metasurface can be redesigned to steer the motion more flexibly.. Kudtarkar said that by adjusting the metasurface layout. it may be possible to guide the metajet “in any way” the design allows. which is the key step toward turning the physics of tiny demonstrations into something practical.
Light sails in space present a particularly demanding problem: steering needs to be achievable without bulky moving parts.. The researchers propose that metasurfaces used in light-sail concepts could allow adjustments to the sail’s behavior by controlling how light interacts with the surface. potentially enabling trajectory correction during flight.
The same general strategy could also be adapted to a biomedical setting, where precise delivery matters.. Kudtarkar suggested that metasurface-based light propulsion could be expanded for space. while the same platforms might also be used to push drugs toward a targeted location.. In that scenario, the appeal is not just steering but also safety and precision.
They point out that lasers used for drug delivery can heat tissues or molecules, potentially causing damage.. With metajets. the team expects that drug-loaded particles would not be directly exposed to the heat and light of the laser beam in the same way. which could help reduce the risk to sensitive molecules.
The researchers are now looking at the next engineering hurdle: making the metajet work with different wavelengths of light. In particular, they want compatibility with the broad spectrum of sunlight, which is what a space light sail would ultimately rely on rather than a single narrow laser line.
The work. while still at an early stage. illustrates how “momentum transfer” can be treated as a controllable design variable rather than a fixed consequence of illumination.. If metasurfaces can be tuned for the lighting conditions of space. the concept of steerable light-driven propulsion could move from a theoretical attraction toward a controllable technology.
As Kudtarkar put it, the idea still feels a bit like science fiction—but the demonstration of controlled, direction-specific motion from a tiny refraction-based metajet suggests the distance between the lab and the cosmos may be shorter than it once seemed, at least in principle.
light sails metasurface metajet interstellar travel laser propulsion space technology drug delivery