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A lens that changes focus with voltage, not motors, in about a quarter of a second

Qurexa Editorial Team27 October 20266 min read 0 0
A lens that changes focus with voltage, not motors, in about a quarter of a second

What happened

On Monday 26 October 2026, researchers in South Korea published a new way to change where a microscope is focused, without moving any part of it. The work appeared in the journal Light: Science & Applications. It came from Pohang University of Science and Technology, known as POSTECH, working with Kyungpook National University. Hongyoon Kim and Eunwoo Park were joint first authors. Junsuk Rho and Chulhong Kim led the research. Their instrument is a photoacoustic microscope. The idea behind photoacoustic imaging is neat: you send in a very short pulse of light, the tissue absorbs it and warms by a tiny amount, and that warming makes it expand very slightly. The expansion makes a faint sound. A sensitive ultrasound detector listens for that sound, and a picture is built from it. It is particularly good at showing blood vessels, because blood absorbs light strongly. Normally, to look deeper or shallower, you physically move the lens. The POSTECH team wanted to avoid that. They used something called a metalens, a flat lens with a pattern of tiny structures on its surface, designed with two focus points. In front of it they put a liquid-crystal cell. When voltage is applied, the cell changes the way the light is twisted, and the lens switches which of its two focus points is active. No motor. No sliding. Just a change in voltage, taking about 0.25 seconds.

Why this matters

Moving parts are the weak point of a lot of precision equipment. They wear out, they need calibration, they add bulk and they take time. In imaging, they also add a very practical problem: if the patient is awake and blinking, every fraction of a second spent mechanically refocusing is a fraction of a second in which the thing you are looking at has moved. Junsuk Rho explained the gain simply. With this design, he said, "we can switch a high-resolution optical focus along the depth direction". He added that "eliminating mechanical motion can also enable more compact and stable imaging systems". Compact and stable matters more than it sounds. A lot of good imaging technology never leaves the research hospital because the equipment is large, delicate and expensive to keep aligned. Anything that removes a moving part moves a technique a little closer to an ordinary clinic. The team also solved a tidier engineering problem. Photoacoustic imaging needs light going in and sound coming out, and the two paths have to line up. They paired the metalens with a ring-shaped ultrasound detector, so the light passes through the middle of the ring. That keeps both axes aligned in a small package. The researchers suggest the approach could be useful for imaging the eye, including in conditions such as diabetic retinopathy, where damage to the small blood vessels at the back of the eye is the thing clinicians need to see.

What the evidence actually says

This was tested in mice, not in people. That is the single most important thing to hold on to. The team used mice with a deliberately induced injury to the cornea, the clear front surface of the eye. In the shallower focus mode, the microscope showed new blood vessels growing into the cornea. In the deeper mode, it resolved vessels near the iris, about 2.2 millimetres below the surface. The measured performance was: a focus switch in about 0.25 seconds, an overall depth range of about 1.2 millimetres, and side-to-side detail of about 3.1 and 3.7 microns at the two focus positions. A micron is a thousandth of a millimetre, so that is fine enough to make out individual small vessels. What that demonstrates is that the optical trick works, and works well enough to produce useful pictures of living tissue. What it does not demonstrate is anything about patients. A mouse eye is small, the animals were anaesthetised, and the injury was created by the researchers rather than being a naturally occurring disease. There is no evidence here about safety in humans, about whether it would find anything a standard eye scan misses, or about cost. The phrase to watch for in coverage of work like this is "could help". It is doing real work in that sentence. The researchers are describing a direction of travel, not a device that is coming to your optician.

Practical advice

None of this changes anything about eye care today, but the condition it mentions is worth taking seriously. If you have diabetes and you live in England, you should be invited for diabetic eye screening at least once every two years, and often yearly. It is a separate appointment from a normal sight test at the optician. The two are not interchangeable, and one does not replace the other. Go when you are invited, even if your sight seems fine. Early damage to the blood vessels at the back of the eye usually causes no symptoms at all. By the time you notice a change, more has been lost than needed to be. If you have diabetes and cannot remember your last screening, ring your GP practice and ask. If you have moved house or changed practice, it is worth checking that you are still on the list. Sudden changes in vision, new floaters, flashes or a dark curtain across your sight are not things to wait on. Contact 111, an eye casualty department or your GP practice the same day. And keep up with blood sugar, blood pressure and cholesterol treatment if you have been prescribed it. That is still the most effective thing anyone can do to protect their sight.

What to know

Researchers at POSTECH in South Korea have built a photoacoustic microscope that changes its focus depth using voltage rather than moving parts, published in Light: Science & Applications on 26 October 2026. It combines a flat metalens with two focus points and a liquid-crystal cell that switches between them when voltage is applied. Switching takes about 0.25 seconds, over a depth range of about 1.2 millimetres, with detail of about 3.1 to 3.7 microns. In mice with an induced corneal injury, it imaged new vessels in the cornea at the shallow setting and vessels near the iris, about 2.2 millimetres down, at the deeper one. This is animal research at an early stage. There is no human data, and no device for clinics yet. The researchers suggest eye imaging, including for diabetic retinopathy, as a possible use. If you have diabetes, the useful action today is simply to attend your diabetic eye screening when invited. It is not the same as a sight test. Sources: Phys.org, "Metalens microscope switches focus with voltage, not moving optics", 26 October 2026, https://phys.org/news/2026-10-metalens-microscope-focus-voltage-optics.html — Light: Science & Applications, 2026, https://www.nature.com/lsa/ — NHS, "Diabetic retinopathy", https://www.nhs.uk/conditions/diabetic-retinopathy/ This article is for general information and does not replace advice from a doctor, optometrist, pharmacist or other qualified healthcare professional. If you notice a sudden change in your vision, seek medical help the same day.

#photonics#medical imaging#metalens#eye health#research#engineering

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