Researchers have found a method that makes it possible to use a full beam of laser light in order to control and move extremely tiny objects, for example - individual cells inside the human body, tiny particles inside chemical test tubes or inside chip devices
[Translation by Dr. Nachmani Moshe]
![One of the researchers activates the laser beam as part of the experiments [Courtesy: Wits University]](https://www.hayadan.org.il/images/content3/2019/02/Nkosi_Bhebhe1-500x250.jpg)
Researchers from the School of Physics at the University of the Watersrand (Johannesburg, South Africa) have found a method that makes it possible to use a full beam of laser light in order to control and move extremely tiny objects, for example - individual cells inside the human body, tiny particles inside chemical test tubes or inside chip devices. Although this method, known as holographic optical trapping and tweezing, is not new, the researchers found a way to utilize the full content of the light beam - including vector light that was not previously accessible within this application. "Previous holographic traps were limited to a certain type of light (scalar light), so it is very exciting that we were able to uncover a holistic device that utilizes all types of light, including the integration of all the trapping devices created in the past," said Professor Andrew Forbes, head of the research team. "We were able to demonstrate the first ever vector holographic optical capture and collection system in the world. The device allows micrometric particles, such as biological cells, to be captured and moved by light alone." The finished device will be able to capture several particles at the same time and move them with a light beam. The research findings have long been published in the scientific journal Scientific Reports.
In conventional optical capture and collection systems, the light is highly focused within a small volume containing small particles, such as biological cells. On such a small scale (usually micro- or nanometers) the forces that light can generate are significant in their intensity, so that the tiny objects can be captured and moved.
The idea behind this standard awarded the American scientist Arthur Ashkin the Nobel Prize in Physics for 2018. Originally, the light was controlled mechanically by mirrors, but the idea was later improved by moving the light holographically, that is, by using computer generated holograms to control the light without using moving parts, thus allowing full control over the particles. Until today, only special types of laser beams, called scalar beams, could be used in such holographic traps. "In particular, our device will be able to operate with normal (scalar) laser beams and also with more complex vector beams. Vector beams are very topical and are used in many applications, but to date no vector holographic trap has been used," explains the lead researcher.
The researchers demonstrated how their new trap enables holographic control of both scalar and vector beams in the same device, a result that advances the forefront of this field while introducing an innovative device to the scientific community. The research group anticipates that the new device could be useful in experiments within the control of micro- and nanometer dimensions, including single-cell studies in biology and medicine, in chemical reactions in a tiny volume, as well as in basic physics for future 'lab-on-a-chip' devices.
In a conventional optical trap, light is tightly focused so that it is able to exert forces on matter. The material, for example, a small particle, is captured within the light beam. When the light is moved by mirrors or mechanical gates, so is the particle trapped within the beam. This process is called optical capture (capture of the particle) and optical collection, that is, moving the particle as if using a picker, but in this case a picker made of light. In order to make control less dependent on mechanical parts, researchers are using holograms to control light. With the help of spatial light modulators, structured light patterns can be coded and these patterns can be moved inside the trap, so that many particles can be trapped and moved at the same moment. This idea opened a window to a host of new fascinating research areas, but the finished holographic optical traps were limited to only scalar beams of light, only a tiny part of the entire spectrum. The other types of optical beams, vector modes, were considered unsuitable for holographic control. With the help of the new vector, today it is possible to use all types of light.
The article describing the study
The news about the study includes a video
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One of the researchers activates the laser beam as part of the experiments [Courtesy: Wits University]
5 תגובות
More accurate 'Johannesburg, South Africa' than 'Johannesburg, South Africa'
DRAP is a country, Southern Africa is a wide area that includes:
South Africa, Botswana, Lesotho, Namibia and Swaziland
Nice, this is really a breakthrough... (for those who didn't understand - I'm being cynical...):
What this publication shows is simply the unification of 3 old and well-known fields in physics (some of which - such as the study of colloidal particles - have been known since the end of the 19th century):
1. Proof that light has momentum (countless articles were published just on this during the years 1905-1921),
2. Use of microfluidic channels to direct the movement of colloids and nanoparticles (studies from the 80s and 90s),
3. Holograms that create temporary microfluidic channels, which can change their shape in the blink of an eye (I will not exaggerate if I write that countless works have been published on this alone from the end of the nineties in the twentieth century to the end of the first decade of the 21st century).
So the bottom line: what's new?!? A nice video is shown here, but it doesn't even show a bar that gives an indication of the size order of the particles and their movement distances (nanometers? microns? hundreds of microns?...)!!! And what is the time scale of the movement of these particles: seconds? hours? days?
In short: very disappointing, and even more disappointing is that this publication also appears here, in the "Hidan" newspaper... too bad.
It's a thread that is interesting how it will affect our lives
Dr. Moshe Nachmani:
The site is popular science, so it will help to add an explanation of what scalar and vector light is...
There is a PhD student in mechanical engineering at the Technion, if I'm not mistaken, who is dealing with this exact thing and has had a few successes