X-ray imaging technology revolutionised the world of medical diagnostics and has found applications in national defence, advanced manufacturing, nuclear technology and environmental monitoring. However, X-ray technology is limited by its high cost, and is associated with safety concerns that stem from the potential for high levels of radiation exposure. Current X-ray machines use inorganic crystals to convert high-energy X-ray photons into visible light, meaning a high dose of X-rays is typically required for effective imaging.

Seeking to resolve this issue, Professor Liu Xiaogang from NUS Chemistry identified nanocrystals made from lead halide perovskite that could serve as an alternative material for X-ray technology. Not only are they less costly than inorganic materials, they are also more sensitive, being able to detect X-rays at a radiation dose 400 times lower than what is typically used in current medical diagnostics. This translates to lower medical expenses and radiation risks for patients.

Prof Liu also seeks to overcome another limitation of existing X-ray machines — their inability to capture curved three-dimensional (3D) objects at high resolution. Currently, detectors in X-ray machines are made of flat panels, generating bulky pixels with low resolution. Prof Liu’s solution sees a flexible X-ray detector made with sodium lutetium fluoride crystals and silicone rubber. This design allows it to be wrapped around 3D objects, and could enable applications such as the detection of defects in electronics, authentication of valuable works of art, and examination of archaeological objects at microscopic scale. His team is currently developing a swallowable X-ray dosimeter for in situ monitoring of absolute absorbed dose, pH and temperature in the gastrointestinal tract.