What if you could use beams of light to trap and manipulate microscopic particles and cells? It sounds like the stuff of science-fiction but it was actually made a reality by Arthur Ashkin in the 1980s.
Here we explore the life and times of Arthur and discuss why his work was so important that he was awarded the Nobel Prize for Physics in 2018.
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Who is Arthur Ashkin?
Arthur Ashkin is a Nobel Prize-winning American physicist who is best known for his invention of a device called optical tweezers. He was born on the 2nd of September 1922 in Brooklyn, New York and is well respected in his field.
He was born into a Ukranian-Jewish family. Between 1942 and 1945, Ashkin joined the U.S. Army and worked at the Columbia Radiation Lab.
Ashkin later enrolled and won his bachelor's in physics from Columbia University, Ithica, New York City in 1947. He later went on to pursue and complete a Ph.D. in nuclear physics at Cornell University in 1952.
Post-doctorate, Ashkin joined Bell Laboratories at Murray Hill. He later moved to their Holmdel, New Jersey facility where he would remain until his retirement in 1992.
It was while working at Bell Labs in New Jersey that Arthur completed his Nobel prize-winning work on lasers.
Despite the technical genius of his work, Ashkin is somewhat modest about his life's work: -
"Well, this is my life's work. It has to do with radiation pressure, the pressure of light. I'm going to give you a little lecture. When light shines on you, it pushes on you. Everybody knows that light has heat. The sun is hot. But the fact is, the sun pushes on you. And with lasers, if you focus the light down to very small spots, you can actually push things or pull, it turns out. Push, pull, make what they call optical traps. So I am the inventor of the optical trap, and it sort of started in that very strange way. Just by accident. " - Arthur Ashkin in an OSA interview.
What did Arthur Ashkin do?
Arthur Ashkin's most prominent work was his pioneering research into optical tweezers. While working at AT & T's Bell Lab in New Jersey, Ashkin was put to work researching microwaves, nonlinear optics, and laser trapping.
As part of his research, Ashkin managed to make the first observation of "continuous-wave (cw) laser harmonic generation, cw parametric amplification, discovered the photorefractive effect, and initiated the field of nonlinear optics in optical fibers." - OSA.org.
In 1970, he was able to use a laser beam to trap and move small transparent beads. Each bead ranged in size from 0.59 to 2.68 microns (1 micron = 10−6 meter).
These beads were suspended in water and when Ashkin shone the light beam on them he found that the beads were not only drawn into the center of the beam but were also pushed along by it. This was an astonishing finding, and quite surprising.
He later found that by using two beams of light of equal intensity and aiming them at one another he could trap and move beads at will. This astounding finding would later lead to Ashkin and his team inventing optical tweezers in 1986.
This device uses a single laser that can focus, using a lens, on a particle and trap it.
Furthermore, one of Ashkin's coworkers, Steven Chu, was able to refine the technique further to trap single atoms. For this work, Chu was awarded the Nobel Prize for Physics in 1997.
Ashkin wanted to use his optical tweezers to study cells, viruses, and bacteria. In order to achieve this, he switched from an infrared light source to green.
This was because green has a less intense beam than infrared and was thus less likely to damage living cells. By making this change, he was able to use his optical tweezers to study the force that molecules used to move organelles around in cells.
Since then, Ashkin et al's optical tweezers have become a widely used technique to study microscopic life and its molecular systems without the risk of killing them.
"Ashkin explored the interior of a cell, manipulating its inner structures, and laying the foundation for new ways to understand normal and diseased states in the human body. The ability to cool and trap atoms has led to spectacular advances in basic science, such as the creation of Bose-Einstein condensates in atomic vapor." - OSA.org.
Ashkin and two of his peers were jointly awarded the Nobel Prize for Physics in 2018.
The reason for his award, according to the Nobel Prize was: -
"The sharp beams of laser light have given us new opportunities for deepening our knowledge about the world and shaping it. Arthur Ashkin invented optical tweezers that grab particles, atoms, molecules, and living cells with their laser beam fingers. The tweezers use laser light to push small particles towards the center of the beam and to hold them there. In 1987, Ashkin succeeded in capturing living bacteria without harming them. Optical tweezers are now widely used to investigate biological systems."
Where is Arthur Ashkin from?
Arthur Ashkin was born in Brooklyn, New York in 1922. He was born into a nativized Ukranian-Jewish family.
"Many consider Ashkin the father of laser radiation pressure. His work in this area concerned the optical trapping and manipulation of small dielectric particles using optical gradient forces. Ashkin achieved a number of “firsts.” He was the first to observe optical gradient forces on atoms and the first to perform laser cooling of atoms known as “optical molasses.” He also was the first to observe optical trapping of atoms." - OSA.org.
Where did Arthur Ashkin go to high school?
Arthur Ashkin attended and graduated from Brooklyn's James Madison High School in 1940. He later went on to attend Columbia University in Ithica, New York to complete his B.Sc. in physics.
After graduating, he then attended Columbia University and prior to that worked as a technician for Columbia's Radiation Lab tasked with building magnetrons for U.S. military radar systems during the Second World War.
Post-graduation he completed his Ph.D. in nuclear physics at Cornell University.
Where does Arthur Ashkin work?
Arthur Ashkin has been officially retired since 1992. Prior to his retirement, he had worked at AT & T's Bell Labs for over forty years.
7 takeaway facts about Arthur Ashkin
1. Arthur Ashkin was born on the 2nd of September 1922 in Brooklyn, New York.
2. He was awarded the Nobel Prize for Physics in 2018 for his invention of optical tweezers.
3. Ashkin is, to date, the oldest person to ever be awarded the Nobel Prize. In an interview with the Nobel Prize, he expressed his relief "because you can't be dead and win".
4. Although Ashkin is officially retired he is still continuing his research. While he considers his work something of a hobby he is currently writing a paper on solar energy.
5. One of Ashkin's heroes is the Dutch scientist, Antonie van Leeuwenhoek. This is the chap who first discovered animalcules, or what we call bacteria and protozoa today.
6. Ashkin has also been enrolled in the National Inventors Hall of Fame in 2013 for his groundbreaking work.
7. "In 1996, Ashkin's basic 1970 paper was cited by the American Physical Society as one of the foremost contributions to atomic physics in the last century." -invent.org. Ashkin also has various other awards and was elected to the National Academy of Science and the National Academy of Engineering.