Science usually advances in small steps. Each new experiment adds a small scrap of information. It’s rare for a simple idea that arises in a scientist’s brain, without the use of any technology, to lead to a significant breakthrough. But that’s what happened to two Israeli engineers who developed a new way to make optical lenses.
The system is simple, cheap and precise, and could have a dramatic impact on up to a third of the world’s population. It could also change the face of space research. And to devise it, all the researchers needed was a whiteboard, a marker, an eraser and a bit of luck.
Prof. Moran Bercovici and Dr. Valeri Frumkin, both from the mechanical engineering department at the Technion – Israel Institute of Technology in Haifa, specialize in fluid mechanics, not optics. But a year and a half ago, at a World Laureates Forum conference in Shanghai, Bercovici happened to be sitting with economist David Zilberman, who is originally from Israel.
Zilberman, a Wolf Prize laureate who is now at the University of California, Berkeley, talked about his research in developing countries. Bercovici described his experiments with fluids. And then Zilberman asked a simple question: “Can you make glasses out of this?”
“Why do you ask?” Bercovici replied. Zilberman’s answer astounded him.
“When you think about developing countries, you usually think about malaria, wars, hunger,” Bercovici says. “But Zilberman said something I was totally unaware of – that there are 2.5 billion people in the world who need glasses but have no access to them. That’s an astounding figure.”
Bercovici returned home and found a World Economic Forum report that confirmed this number. Although making a simple pair of glasses costs just a few dollars, in large parts of the world, cheap glasses are neither made nor sold.
The impact is enormous, from children who can’t see the blackboard in school to adults whose vision deteriorates so badly that they lose their jobs. And besides the harm to people’s quality of life, the cost to the global economy has been estimated at $3 trillion a year.
Bercovici couldn’t sleep at night after the conversation. When he arrived at the Technion, he discussed the issue with Frumkin, who was then a postdoctoral researcher in his lab.
“We drew a lens on the whiteboard and looked at it,” he recalls. “We knew instinctively that we couldn’t make this shape with our technique for controlling fluids, and we wanted to find out why.”
The answer, he says with a smile, “was that annoying thing called gravity.”
Spherical shapes are the basis for optics, since lenses are made from them. In theory, Bercovici and Frumkin knew that they could take polymers, which are liquids that have solidified, and make round domes from them, thereby creating lenses. But liquids maintain a spherical shape only at tiny volumes. At larger volumes, the force of gravity flattens them into a puddle.
“So what we had to do was get rid of gravity,” Bercovici explains.
And that’s exactly what he and Frumkin did. After studying their whiteboard, Frumkin came up with an idea so simple it’s not clear why nobody ever thought of it before – you can eliminate the effect of gravity if you make the lens inside a liquid chamber. All you have to do is make sure the liquid in the chamber, called the buoyancy liquid, has the same density as the polymer from which you are making the lens, and then the polymer will float.
The other essential thing is to use two fluids that are immiscible, meaning they don’t mix with each other, such as oil and water. “Most polymers are more like oils, so our ‘exotic’ buoyancy liquid is water,” Bercovici said.
But since water has a lower density than polymers, its density has to be increased a little so the polymer will float. For this, too, the researchers used not-so-exotic materials – salt, sugar or glycerin.
The final ingredient in the process, Bercovici says, is a rigid frame into which the polymer is injected, enabling control over its form.
When the polymer reaches its final form, it is hardened using UV radiation and becomes a solid lens. To create the frames, the researchers used a simple sewage pipe sliced into rings, or Petri dishes from which they had cut off the bottom. “Any kid could make them at home, and I made some at home with my daughters,” says Bercovici. “We have made a lot of things in the lab over the years, some of them very complex, but this without a doubt was the simplest and most unsophisticated thing we ever did. And perhaps the most important.”
Small, ugly and incredible
Frumkin created his first lens on the same day that he thought of the solution. “He sent me a photo on WhatsApp,” Bercovici recalls. “In retrospect, it was a pretty small and ugly lens, but we were delighted.” Frumkin kept on examining the new invention. “The equations showed that once you remove gravity, it doesn’t matter if the frame is one centimeter in size or one kilometer; you will always receive the same shape, depending on the amount of material.”
The two researchers continued with their experiment with the second generation of secret ingredients – a mop bucket – and used it to create a lens with a diameter of 20 centimeters, suitable for a telescope. The cost of lenses grows exponentially by diameter, but with this new method all that is required, regardless of size, is a cheap polymer, water, salt (or glycerin) and a ring-shaped mold.
The list of ingredients marks a dramatic turn from the traditional lens-making method that has remained almost unchanged for 300 years. In the initial stage of the traditional process, a slab of glass or plastic is ground down mechanically. In the manufacture of lenses for glasses, for example, some 80 percent of the material goes to waste. Using the method devised by Bercovici and Frumkin, instead of grinding down solid material, liquid is injected into a frame, creating a lens in a completely waste-free process. This method also removes the need for polishing, as the surface tension of the fluid ensures the creation of an extremely smooth surface.
Haaretz visited the lab at the Technion, where doctoral student Mor Elgarisi demonstrated the process. He injects polymer into a ring inside a small liquid chamber, shines a UV lamp on it, and after two minutes hands me a pair of surgical gloves. Very carefully, I dip my hands into the water and pull out the lens. “That’s it, process over,” Bercovici shouts out.
The lens is absolutely smooth to touch. It’s not just a subjective feeling: Bercovici says that even without polishing, the surface roughness of a lens manufactured using the polymer method is less than a nanometer (one billionth of a meter). “The forces of nature create extraordinary quality by themselves, for free,” he says. By comparison, optical glasses are polished to a level of 100 nanometers, while the mirrors on NASA’s flagship project, the James Webb Space Telescope, are polished to a level of 20 nanometers.
But not everyone is convinced that this elegant method will be the savior for billions of people around the world. Prof. Ady Arie of the School of Electrical Engineering at Tel Aviv University notes that Bercovici and Frumkin’s method requires a circular mold into which the liquid polymer is injected, the polymer itself, and a UV lamp.
“These aren’t available in villages in India,” he notes. Another problem raised by Niv Adut, founder and VP of R&D at SPO Precision Optics, and by the company’s chief scientist, Dr. Doron Sturlesi – who are both familiar with Bercovici's work – is that replacing the grinding process with a plastic cast will make it difficult to adapt the lens to the person who needs it.
Bercovici isn’t alarmed. “Criticism is a fundamental component of science, and our rapid development over the past year was achieved in great measure thanks to experts who pushed us into a corner,” he says. Regarding the feasibility of manufacturing in remote regions, he adds: “The infrastructure required to create glasses using the traditional method is enormous; you need a factory, machines, technicians, while we require only minimal infrastructure.”
Bercovici shows us two UV radiation lamps in his lab: “This one came from Amazon and cost $4, while the other came from AliExpress and cost $1.70. And if you don’t have them, you can always use sunlight,” he explains. And what about the polymer? “A 250-milliliter bottle costs $16 on Amazon. The average lens requires between five to 10 milliliters, so the cost of the polymer isn’t really a factor either.”
He emphasizes that his method also doesn’t require a unique mold for each lens number, as critics have claimed. The simple mold is suitable for each lens number, he explains: “What makes the difference is the amount of polymer injected, and to create a cylinder for glasses all that is required is to stretch the mold a little bit.”
The only expensive part of the process, says Bercovici, is automation of the polymer injection, which has to be done precisely according to the lens number required.
“Our fantasy is to create an impact in countries with minimal resources,” says Bercovici. While it is possible to bring cheap glasses to poor villages – even though this has yet to be done – his plans are much bigger. “Just as in the well-known proverb, I don’t want to give them fish, I want to teach them how to fish. With this method, people will be able to make their own glasses,” he says. “Will it succeed? Only time will tell.”
Lenses are just the first stage
Bercovici and Frumkin described the process about six months ago in an article in the first edition of Flow, a journal on the application of fluid mechanics, published by Cambridge University. But the team doesn’t plan to stop at simple optical lenses. Another paper published a couple of weeks ago in the journal Optica describes a way to use the new method to create complex optical components in a field known as freeform optics. These optical components are neither convex nor concave, but instead are shaped as topographic surfaces, with light hitting the surface in different areas to achieve the desired result. Such parts can be found in multi-focal glasses, pilot helmets, advanced projector systems, virtual and augmented reality systems, and elsewhere.
The manufacture of freeform components using sustainable methods is complex and expensive, as it is very hard to grind and polish their surface areas. As a result, these parts have limited use at present. “There have been academic publications about the possible uses of such surfaces, but this has yet to be reflected in practical use,” explains Bercovici. In the new paper, the lab team headed by Elgarisi showed how control over the form of the frame enables control over the form of the surface created when a polymer liquid is injected. The frame can be created with a 3D printer. “We no longer make do with a mop bucket, but it’s still simple,” says Bercovici.
The lab’s research engineer, Omer Luria, notes that the new technology enables rapid production of particularly smooth lenses, with unique topographies. “We expect it to dramatically reduce both the cost and production time of complex optical parts,” he says.
Prof. Arie is one of the editors of Optica, but wasn’t involved in the review of the article. “It’s very nice work,” Arie says of the study. “In order to produce aspherical optical surfaces, current methods use molds or 3D printing, but with both methods it is difficult to create sufficiently smooth and large surfaces within a reasonable timeframe.” Arie believes that the new method will help create prototypes of freeform components. “For industrial production of large quantities of parts, it’s preferable to prepare molds, but in order to rapidly test new ideas this is an interesting and elegant method,” he says.
SPO is one of Israel’s leading companies in the field of freeform surfaces. According to Adut and Sturlesi, the new method has advantages and disadvantages. They say that the use of plastics restricts possibilities, as they are not durable in extreme temperatures and are limited in their ability to achieve sufficient quality on the complete range of colors. As for advantages, they note that the technology has the potential to significantly reduce the cost of production of complex plastic lenses, which are used in all cellphones.
Adut and Sturlesi add that with traditional manufacturing methods, plastic lenses are restricted in diameter, as the larger they are, the less precise they become. They state that creating the lenses inside a liquid, as per Bercovici’s method, prevents distortion and thus enables creation of very powerful optics – whether in the field of spherical lenses or freeform lenses.
It’s all about people
It was the option of producing large lenses that led to the Technion team’s most unexpected project. Here too, it all began with a chance conversation and an innocent question. “It’s all about people,” says Bercovici. He was telling Dr. Edward Balaban, a research scientist for NASA, whom he knew from their days together at Stanford University, about his project, when he asked Berkovici: “Do you think you could produce a lens like that for a space telescope?”
“It sounded like a crazy idea,” recalls Bercovici, ” but it stuck in my mind.” After the lab tests were completed successfully, the Israeli researchers realized that the method could work in the same way in space. After all, you can achieve microgravity conditions there, with no need for a buoyancy liquid. “I called Edward and I said to him, this could work!”
Space telescopes have a big advantage over terrestrial ones, as they are not affected by the atmosphere or light pollution. The biggest problem in developing space telescopes is that their size is limited by the size of the launcher. While on Earth, telescopes currently have a diameter of up to 40 meters. The Hubble space telescope has a mirror with a 2.4-meter diameter, and the James Webb telescope has a mirror with a 6.5-meter diameter – an achievement that took scientists 25 years to reach at a cost of $9 billion, partly because of the need to develop a system that would enable launch of the telescope in a folded position and then automatically open it in space.
Liquid, on the other hand, already comes in a “folded” state. One could for example fill the launcher with a liquid metal, add an injection mechanism and an expanding ring, and produce the mirror in space. “It is a fantasy,” admits Bercovici. “My mother asked me, ‘When will it be ready? I told her, ‘Perhaps in about 20 years.’ She said she doesn’t have time to wait.”
If this dream were to come true, it could change the future of space research. Today, notes Bercovici, humanity doesn’t have the ability to look directly at exoplanets – planets outside of the solar system, because to do so would require Earth-based telescopes 10 times bigger than those that exist right now – something that is completely impossible with existing technologies.
On the other hand, Bercovici adds, the biggest space launcher currently around, SpaceX’s Falcon Heavy, can carry 20 cubic meters of liquid. Theoretically, he explains, the Falcon Heavy could be used to launch the liquid to an orbit point where the liquid could be used to produce a mirror with a 75-meter diameter – one that would be 100 times larger in surface area and light collected than the James Webb telescope.
It is a dream, and making it come true will take a long time. But it is being taken seriously by NASA. Together with a team of engineers and scientists from NASA’s Ames Research Center, led by Balaban, first attempts are being made to implement the technology.
In late December, a system developed by the team at Bercovici's lab to enable astronauts to produce and solidify lenses in space will be sent to the International Space Station, where a series of experiments will be conducted. Prior to that, experiments will be conducted this weekend in Florida to examine the feasibility of producing a high-quality lens in microgravity without any need for a buoyancy liquid.
The Fluidic Telescope Experiment (FLUTE) is carried out in a reduced-gravity aircraft – a plane that has had all its seats removed and is used for training astronauts, and for filming zero-gravity scenes in movies. By maneuvering in the form of an inverse parabola – ascent followed by a free fall – conditions of microgravity are created within the plane for a short time. “It is known as ‘the vomit comet’ for good reason,” Bercovici says with a smile. The free-fall lasts for about 20 seconds in which gravity in the plane is close to zero. During this time the researchers will try to create a liquid lens and to carry out measurements to prove that the lens is of sufficient quality before the plane straightens out, gravity returns with full force, and the lens becomes a puddle.
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The experiment was scheduled for Thursday and Friday with two flights, each conducting 30 parabolas. Bercovici and most of the lab team, including Elgarisi and Luria, will be there, as will Frumkin, who will arrive from the Massachusetts Institute of Technology.
During my visit to the Technion lab, the excitement was palpable. Laid out on the floor were 60 cardboard boxes containing 60 small, self-produced kits to be used for the experiment. Luria was conducting final, last-minute improvements on the computerized experimental system he developed to measure performance of the lenses.
Meanwhile, the team was conducting timed practice runs ahead of the moment of truth. One of the team stands there with a stopwatch and the others have 20 seconds to produce a lens. On the plane itself, conditions will be much harsher, especially after a few free-falls and upward lifts in increased gravity conditions.
It isn’t just the Technion team that is excited. Balaban, principal investigator of the NASA FLUTE Experiment, told Haaretz that “the fluidic shaping approach could potentially lead to powerful space-constructed telescopes with apertures measuring in tens or even hundreds of meters. Such telescopes may, for instance, enable direct observations of planets around other stars, facilitating high-resolution analysis of their atmospheres and perhaps even recognition of large-scale surface features. The approach could lead to other space applications as well, such as in-space manufacturing of high-quality optical components for energy collection and transmission, scientific instruments, and medical devices — thus playing an important role in the emerging space economy.”
Shortly before boarding the plane for the adventure of his lifetime, Bercovici pauses for a moment in amazement. “I keep asking myself how no one figured this out before,” he says. “Every time I go to a conference, I’m afraid that someone will stand up and say that some researcher in Russia did this 60 years ago. After all, it’s such a simple method.”