The principle of optical traction is to move an object over a distance. The concept is widely used in science fiction films. It also exists in reality… but on a much smaller scale. Instruments such as optical tweezers, for example, can manipulate microscopic particles using lasers. Today, researchers claim to have succeeded in creating a tractor beam capable of moving macroscopic objects.
Light has both energy and momentum which can be used for various optical manipulations, such as levitation and rotation. In the last ten years, optical traction of micro- and nano-objects (cells, atoms, nanoparticles, etc.) has thus been demonstrated on several occasions. It is still used frequently today in biology and nanotechnology. Optical traction of a macroscopic object, on the other hand, is much more complex to implement, as it obviously requires a lot of power.
A team from the Qingdao University of Science and Technology in China announced that it had achieved this feat and presented its tractor beam in the journal Optics Express, , In previous studies, the pulling force of light was too weak to pull a macroscopic object. With our new approach, the magnitude of the pulling force is enormous. In fact, it is more than three orders of magnitude greater than the light pressure used to drive a solar cell, which uses photon momentum to exert a tiny pushing force. said Lei Wang, first author of the study.
Ability to take vehicles to Mars
The tractor beam graphene and silica (SiO2): the front layer was composed of cross-linked graphene and the back layer of SiO2, This material was used on a torsion pendulum, through which the researchers were able to demonstrate the phenomenon of laser traction in a manner visible to the naked eye. They also used a gravitational pendulum to quantitatively measure the pulling force of the laser; Both instruments were about five centimeters long.
When an object is irradiated by a laser beam, the gas molecules behind the object gain more energy and, therefore, “push” the object toward the light source. This effect, combined with the low pressure (5 Pa) of the environment in which the experiment was performed, induces displacement of the object. The tensile force (0.8 µN) was much higher than the radiation pressure (about 0.28 nN); It can also be adjusted by modulating the power of the laser.
However, it should be noted that the composite object was specifically designed for the experiment and took place under very specific laboratory conditions (at low atmospheric pressure).
If the effectiveness of this tractor beam on Earth is compromised for the time being, it may prove useful on other planets:” The rarefied gas environment we used to demonstrate the technique is similar to that found on Mars. Therefore, she may one day have the ability to manipulate vehicles or aircraft on Mars. Wang says.
A technology that still needs improvement
The researchers point out that many aspects of the technology still need to be improved before it becomes truly usable. For starters, the team needs its tractor beam to work over a wide range of air pressures. Furthermore, it is necessary to establish a theoretical model to accurately predict the laser pulling force depending on various parameters (such as object geometry, laser energy and surrounding medium).
In the meantime, their study constitutes a solid proof of feasibility. , Our work demonstrates that flexible manipulation of a macroscopic object by light can be achieved when the interactions between light, object and medium are carefully controlled. Wang said. This study also highlighted the complexity of laser-matter interactions and the fact that many phenomena at both the macro and micro scales are still far from being fully understood.
Namely that NASA has already considered using tractor beams to collect samples of Mars, explains universe today, The Curiosity rover is equipped with a spectroscopic analysis tool inspired by laser ablation, ChemCam: A laser vaporizes rock, then the resulting plasma is analyzed remotely by spectroscopy. However, if a tractor beam were able to attract the regolith particles directly into the rover, a more complete analysis would be possible.
In the same way, these beams can be used to collect particles from the tails of comets or from clouds in Earth’s atmosphere or from other planets. The concept therefore has important implications for space exploration.
