Organic semiconductors are set to lay the foundation for a new form of flexible X-ray detectors. The flexibility offers the prospect of lower radiation levels and more accurate imaging. Feng Gao heads the project, which aims to produce a prototype within five years.
Project Grant 2024
Flexible X-ray detectors based on novel high-Z covalent organic frameworks
Principal Investigator:
Feng Gao, Professor of Optoelectronics
Co-investigators:
Linköping University:
Mats Fahlman
Chalmers University of Technology:
Eva Olsson
Uppsala University:
Sascha Ott
Institution:
Linköping University
Grant:
SEK 31,000,000 over five years
X-ray technology was invented as far back as the late 19th century. Today, it has a wide range of uses, including security checks at airports, crack inspection in airplanes, and quality control in high-end chips. In healthcare above all, Wilhelm Röntgen’s invention has had a revolutionary impact.
But quite a high radiation level is still required to produce a detailed image of a damaged knee or a broken ankle. If the X-ray detector could be placed closer to the body, the radiation level could be greatly reduced while maintaining the same high image resolution.
“Some injuries make it harder to get a clear X-ray image because current detectors are rigid. If we could wrap the detector around a part of the body, it would be easier to make a more precise diagnosis. Proximity to the injury also makes it possible to reduce radiation levels and relieve patient discomfort,” says Gao, professor of optoelectronics at Linköping University.
Organic detectors
Gao heads a project funded by Knut and Alice Wallenberg Foundation with the aim of developing a new type of X-ray detector based on organic semiconductors which are carbon-based compounds. The result is a plastic-like material that enables thin, flexible, and lightweight electronics.
An X-ray detector made entirely of organic materials could be wrapped around the body like a bandage. Feng Gao elaborates:
“The dilemma is that organic semiconductors cannot effectively absorb X-rays in the same way as current detectors.”
Current X-ray equipment captures X-rays and converts them into images using a type of bulky and rigid inorganic materials. To capture X-rays using organic semiconductors, the researchers need to add heavier elements. Lead is one of the most effective metals for absorbing radiation, but it is highly toxic. Instead, the project team plans to use heavy elements with low environmental risks, such as bismuth.
Integrating heavy elements into the organic semiconductors retains flexibility while giving the material the ability to capture X-rays.
“The main challenge is finding ways to evenly distribute the heavy elements throughout the organic materials. We need to achieve a good chemical balance between the metal and the organic components.”
Current X-ray images are similar to traditional photographic negatives. Dense materials, such as bones, show up as bright areas in the image. Darker areas correspond to soft tissue that lets more radiation pass through to the detector. The radiation is converted into electrical signals that build a radiographic image, revealing, for example, a broken foot to the examining physician.
Strong teamwork
Gao stresses that strong teamwork is vital to achieve the goal of a flexible X-ray detector:
“The key is that we have four strong research teams that will be working more or less hand in hand with each other.”
At Uppsala University, Sascha Ott’s team is contributing expertise on which organic materials are best suited to tailor the light-capturing and electrical conductivity functions. Eva Olsson’s research team at Chalmers University of Technology investigates that the heavy metal is evenly distributed in the material, using specialized transmission electron microscopy.
Gao’s colleague Mats Fahlman at Linköping University is characterizing the material itself, i.e., describing its optoelectronic properties to understand how it behaves under different conditions. In addition to capturing X-rays, the material must retain good electrical conductivity to provide sufficiently high-resolution images.
“We will be working very closely together to take steps toward developing a material with the right traits. If all goes well, we hope to present a prototype within five years.”
Cheaper technology
Thanks to the use of organic semiconductors, flexible detectors could be cheaper to manufacture than current detectors. Organic electronics are built from carbon-based molecules, making them more resource-efficient than silicon, for example.
“In the long run, it might also be possible to create patterns in the organic material that further enhances X-ray absorptions. But first we need to create a material with the right properties.”
If the researchers manage to develop a material with high absorption capacity, the radiation dose can be reduced without compromising image quality. This would greatly benefit healthcare professionals, who currently need to use protective equipment during examinations or leave the room entirely.
“As part of the project, we will involve medical personnel so we can learn how they might use more flexible X-ray detectors. We don’t want to create just another device; we want to develop a technology that genuinely improves healthcare,” says Gao.
Text Magnus Trogen Pahlén
Translation Maxwell Arding
Photo Magnus Bergström
