Arthur Ashton’s Serendipitous Invention of Optical Tweezers

(p. B11) Arthur Ashkin, a physicist who was awarded a 2018 Nobel Prize for figuring out how to harness the power of light to trap microscopic objects for closer study, calling his invention optical tweezers, died on Sept. 21 [2020] at his home in Rumson, N.J.

. . .

Dr. Ashkin’s discovery was serendipitous.

In 1966, he was head of the laser research department at Bell Labs, the storied New Jersey laboratory founded by the Bell Telephone Company in 1925, when he went to a scientific conference in Phoenix. There, in a lecture, he heard two researchers discuss something odd that they had found while studying lasers, which had been invented six years earlier: They had noticed that dust particles within the laser beams careened back and forth. They theorized that light pressure might be the cause.

Dr. Ashkin did some calculations and concluded that this was not the cause — it was most likely thermal radiation. But his work reignited a childhood interest in the subject of light pressure.

Light pushes against everything, including people, because it comprises tiny particles called photons. Most of the time the pressure is utterly insignificant; people, for one, feel nothing. But Dr. Ashkin thought that if objects were small enough, a laser might be used to push them around.

. . .

Then, in 1986, he and several colleagues, notably Steven Chu, achieved the first practical application of optical tweezers when they sent a laser through a lens to manipulate microscopic objects. Their results were published in another paper in Physical Review Letters. Dr. Chu began using the tweezers to cool and trap atoms, a breakthrough for which he was awarded a one-third share of the Nobel Prize in Physics in 1997.

Dr. Ashkin, it was clear, was irked that the Nobel committee had not recognized his foundational work in awarding the prize. But he had already begun to use the tweezers for a different purpose: trapping live organisms and biological material.

Other scientists thought this application would not work, as he explained in an interview with the Nobel Institute after he was awarded the prize in 2018.

“They used light to heal wounds, and it was considered to be deadly,” he said. “When I described catching living things with light, people said, ‘Don’t exaggerate, Ashkin.’”

. . .

Dr. Ashkin was awarded one-half the 2018 physics prize, . . . . In so doing he became, at 96, the oldest recipient of a Nobel Prize at the time.

. . .

Dr. Ashkin’s retirement from Bell Labs did not stop him from continuing his research. When he received word of his Nobel Prize, he was working on a project in his basement to improve solar energy collection. Asked if he was going to celebrate, he said: “I am writing a paper right now. I am not about celebrating old stuff.”

For the full obituary, see:

Dylan Loeb McClain. “Arthur Ashkin, 98, Dies; Nobel-Winning Physicist.” The New York Times (Tuesday, September 29, 2020): B11.

(Note: ellipses, and bracketed year, added.)

(Note: the online version of the obituary was updated Oct. 5, 2020, and has the title “Arthur Ashkin, 98, Dies; Nobel Laureate Invented a ‘Tractor Beam’.”)

The essay about Aoyagi mentioned above is:

Severinghaus, John W. “Takuo Aoyagi: Discovery of Pulse Oximetry.” Anesthesia & Analgesia 105, no. 6 (Dec. 2007): S1-S6.

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