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Researchers use electrically responsive fluid to make eye-like adaptive lenses

Researchers use electrically responsive fluid to make eye-like adaptive lenses
Researchers developed an adaptive liquid lens based on a new electrically responsive fluid called dibutyl adipate (DBA). The new lens changes shape and thus focal length when a voltage is applied. Credit: Miao Xu, Hefei University of Technology

Researchers have developed an adaptive liquid lens based on a new electrically responsive fluid called dibutyl adipate (DBA) that changes focal length when a voltage is applied. The lens is light, compact and simple to manufacture, making it ideal for mobile phone cameras, endoscopes, glasses and machine vision applications.

"The human eye can arbitrarily focus on objects at different distances at incredibly high speeds," said research team leader Miao Xu of Hefei University of Technology in China. "Inspired by this functionality, we developed an eye-like adaptive fluid lens that can be used to diverge or converge light by changing the shape of the DBA fluid."

In the journal Optica Publishing Group Optics letters, the researchers describe their new DBA-based adaptive liquid lens, which weighs only a few grams, and shows that it exhibits high optical performance with good stability. The electronegative molecular structure of DBA makes it possible to use an applied voltage to rapidly change the shape of the lens to change its focal length. DBA is also transparent, non-volatile and inexpensive, making it ideal for use in adaptive liquid lenses.

"This type of adaptive liquid lens could one day replace conventional solid-lens systems," Xu said. "This would enable a cell phone camera that can quickly change focal length while still being as thin as the phone itself." Because it does not require any mechanical elements, this type of lens can be used for years without getting worn.

To turn liquid into a lens

The researchers created the new liquid lens by filling an electrode with DBA liquid, which forms a dome shape because the inner surface of the electrode is coated with a water-repellent layer. Applying a direct current causes the DBA molecules to accumulate at the anode, changing the dome shape in a way that is dependent on the applied voltage, thus changing the focal length. Removal of the electric field causes the DBA liquid to regain its original shape.

The DBA lens offers a significant improvement over commercially available adaptive liquid lenses that are commercially available. Electrowetting liquid lenses use a liquid, such as saline, which requires a dielectric film to separate the conductive liquid from the metal electrode.

"Our DBA liquid lens is not susceptible to evaporation or electrolysis, and because the DBA liquid comes in direct contact with the electrode, there is no need for an insulating layer," Xu said. "This gives the DBA lens a simpler structure and better stability compared to a liquid lens for electro-humidification."

The focal length of the new DBA liquid lens can be changed by increasing the applied voltage. The film shows this process at 10x the normal speed. Credit: Miao Xu, Hefei University of Technology

Demonstrate optical performance

Analysis of the new DBA-based liquid lenses showed that they exhibit an optical transmittance of about 95% at visible wavelengths between 390 and 780 nm, and that the performance remains stable at temperatures from room temperature to above 200 ° F. The researchers also showed that increasing the applied voltage from 0 to 100 V changed the focal length from 7.5 mm to 13.1 mm and that the lens resolution can reach almost 29 lines per. millimeter.

Researchers continue to work on making the new lenses more practical by developing ways to reduce the voltage required to operate the DBA-based liquid lens, increase resolution, and improve the response speed by the order of milliseconds. They also want to reduce the impact of gravity on the DBA fluid so that larger lenses can be made.


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More information: Miao Xu et al, liquid lens with variable focus based on electrically responsive liquid, Optics letters (2021). DOI: 10.1364 / OL.447182
Provided by The Optical Society

Citation: Researchers use electrically responsive fluid to make eye-like adaptive lens (2022, January 19) Retrieved January 20, 2022 from https://phys.org/news/2022-01-electrically-responsive-fluid-eye-like-lens . html

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