It hits with a beam: a controlled lens will create a "harmless X-ray"
Russian scientists have developed a "smart" lens that allows them to control terahertz radiation that is safe for living cells. The novelty can become the basis for a "harmless X-ray" with high-detail images, and its ability to change properties under the influence of electricity opens the way to the creation of portable devices for imaging tumors in various modes of operation. Experts note that the development is able to bring laboratory technologies to the level of practical application in medicine so far.
A lens for "harmless X-rays"
MIPT specialists, together with colleagues from Skoltech, ITMO, IOF RAS, IFT RAS, and scientific centers in China and the United Arab Emirates, have created a lens capable of dynamically changing the intensity of terahertz radiation. Such electromagnetic waves easily pass through non-metallic materials without causing any harm to living cells. Therefore, the optical element that allows them to be controlled opens up the possibility of creating a harmless X-ray analogue.
— The terahertz wavelength range remains one of the least studied areas of the electromagnetic radiation spectrum. This creates a shortage of the element base needed to focus the radiation. The existing systems use static lenses with preset parameters of intensity, focus, etc. The main purpose of our work was to be able to dynamically control the lens, which will allow us to create adaptive optics for medicine. For example, imagine a medical device that pulses radiation and allows you to study the reaction of biological tissues to terahertz radiation power," said Maria Burdanova, senior researcher at the Center for Photonics and 2D Materials at MIPT.
Terahertz waves are located in a special "niche" of the electromagnetic spectrum. They easily penetrate through non-metallic materials, while remaining absolutely safe for living cells. This property makes them a safe alternative to X-rays, allowing them to "look" inside the body without causing harm.
However, there are still no compact and flexible terahertz wave control systems in the world, including dynamically adjustable lenses. Existing radiation focusing devices are static and bulky structures with rigidly defined manufacturing properties. To overcome these limitations, scientists have developed an ultrathin lens based on carbon nanotubes that can flexibly change its optical characteristics.
Single-walled carbon nanotubes in the laboratory
— Carbon nanotubes are not the only material that can change the characteristics of a lens. Nevertheless, compared with other "candidates", nanotubes look like an optimal and promising solution in terms of their combined properties. Our team has managed to customize the material at different levels, from atomic packaging to a new and one—step method of creating patterns, which opens up amazing opportunities for our science and technology in the future," said Dmitry Krasnikov, senior lecturer at Skoltech.
In the new lens, the light is directed by a set of concentric rings. Like filters, they let through only those waves that, adding up and amplifying each other, create a clear and focused point. It is possible to change the optical properties of the invention using a small voltage: if only -2 to +2 volts are applied to the contacts, the ions in the liquid begin to move, creating a double layer, as in a capacitor, "pumping" a film of nanotubes with electric charges. This makes it more "transparent" or "opaque" to terahertz waves. As a result, it is possible to remotely and smoothly adjust the intensity of the beam in focus in the range from -20 to +15%.
Scientists have already created and successfully tested a prototype in the laboratory and patented the invention. They are currently working to increase the system's response rate by experimenting with other types of electrolytes. In the future, they plan to create multi-layered lens structures with multiple independently controlled foci.
In addition to medical diagnostics, lenses can be used in telecommunications, as the gigantic terahertz bandwidth can be used for 6G cellular communication devices, the speed of which is tens and hundreds of times higher than that of 5G.
New diagnostic devices
The developed lens based on carbon nanotubes is ideally suited for creating diagnostic devices and imaging systems, Alexey Chernykh, senior researcher at the ITMO Photonics and Optoinformatics Research Center, told Izvestia.
— Unlike passive static lenses, our development is a programmable and tunable optical element. It is capable of replacing several mechanical or optical components, such as scanners or interchangeable lens kits. This directly leads to a simplification of the device's design, an increase in its reliability and a reduction in cost," said the specialist.
According to him, the resolution of classical optical systems is limited by their fundamental properties, and a new development can overcome this limit and thereby see previously hidden details.
Terahertz radiation does not ionize tissues, so it is safe for long-term and frequent monitoring of living objects. The main advantage of the developed lens is its adaptability and controllability: using the application, you can quickly change the intensity of focus, which opens up new prospects for the development of intelligent diagnostic systems, says Valery Tuchin, the world's most cited scientist in the field of biophotonics, head of the Department of Optics and Biophotonics at SSU, winner of the national prize in the field of future technologies "Challenge".
"For example, for the study of biological tissues, a lens—based device can first reduce the intensity for a wider view and find an area with pathology, and only then highlight the necessary area at the optimal intensity to obtain the clearest and most contrasting image of the boundaries and internal structure of the tumor," said the scientist.
It is important for biomedical applications that such compact lenses can be integrated into hybrid circuits with waveguides and endoscopes. This will make it possible to create portable devices for imaging tumors and conducting biological research at the cellular level, he added.
According to Anton Averyanov, CEO of the ST IT Group of companies, TechNet NTI market expert, the new lens accelerates the transition of terahertz waves from laboratories to practice, solving the problem of lack of a hardware base and opening the way to compact devices in medicine, communications and security.
And according to Leonid Drobyshevich, an NTI technology expert, due to its low energy, terahertz radiation can be used in scanners of control systems for visualization and detection of prohibited objects and substances.
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