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A top international research team led by City University of Hong Kong (CityU) has been awarded HK$28 million by the Theme-based Research Scheme (TRS) of the Research Grants Council (RGC) for the design of a compact and affordable terahertz system that can be used to detect contaminants in food and drugs, and also cancerous cells and tumours.

Terahertz (THz) waves exist in the electromagnetic spectrum between conventional microwaves and infrared regions, and have a broad range of applications.

“THz spectroscopy has been applied successfully to detect contaminants in food and drugs. For example, it can differentiate plant oils and animal fats because their refractive indices and absorption rates vary differently with increasing frequency and temperature,” explained Professor Chan Chi-hou, Project Coordinator, Chair Professor of Electronic Engineering and Director of the State Key Laboratory of Millimeter Waves (SKLMW) at CityU.

“It could also be used in the detection of melamine in milk powder, antibiotics in food matrices, pesticides in vegetables, and foreign objects in drugs,” he added.

“In addition, THz imaging techniques are useful in diagnosing cancers as a higher water content and structural changes such as increased cell and protein density in tissues with tumours result in larger THz absorption and refractive index for tissues. These waves can provide useful information about the structures of proteins and identify specific molecules based on their spectral features,” commented Professor Kenneth Lo Kam-wing, a co-principal investigator.  

Dr Alex Wong Chun-yuen, one of the team members, added, “THz spectroscopic techniques can also be utilised to study the weak interactions between small molecules, which may be difficult to examine by other means.”

However, existing THz systems are bulky and expensive. A low-cost, portable THz system for imaging and spectroscopy can not only accelerate THz research but also resolve food safety and health issues. Material scientists on the team, Dr A L Roy Vellaisamy and Dr Johnny Ho Chung-yin, will investigate polymer based photoconductive devices incorporated with semiconductor nanowires to drive down the cost and enhance the THz conversion efficiency.

“We have assembled an international, multidisciplinary team to develop highly efficient THz sources and detectors, fast beam scanning devices for data acquisition, signal processing and imagery display for the proposed compact system,” said Professor Chan.

The research team also expects to develop electronic scanning techniques for fast image acquisition, near-field measurement techniques to enhance image resolution, display technology for and enhance the sensitivity of THz imaging; and create libraries of THz spectral signatures of chemicals and proteins.

To speed up the progress, research on biomedical imaging, chemical spectroscopy, and imagery display will be simultaneously carried out using existing and currently built THz systems while the compact system is being developed. 

Dr Wong Hang, a young member on the team, is excited about new opportunities this synergistic multidisciplinary project may bring to the team.

The project, titled “A Compact System for Terahertz Imaging and Spectroscopy”, is a joint-institutional effort led by CityU in collaboration with the University of Hong Kong; University of Electronic Science and Technology of China; University of California, US; University College London; and University of Limoges, France. 

For this round of TRS, RGC added a new category "Advancing Emerging Research and Innovations Important to Hong Kong" on top of the existing three themes. Out of the 21 proposals submitted, this is one of only two proposals that was eventually awarded funding for the innovation theme.

The team comprises one project coordinator, seven co-principal investigators and nine collaborators from CityU. They are:
?  Chair Professor Chan Chi-hou, Project Coordinator, Department of Electronic Engineering (EE) & SKLMW;
?  Chair Professor Edwin Pun Yue-bun, EE & SKLMW;
?  Chair Professor Xue Quan, EE & SKLMW;
?  Chair Professor Luk Kwai-man, EE & SKLMW;
?  Chair Professor Stella W. Pang, EE & SKLMW;
?  Chair Professor Jeffrey Shaw, School of Creative Media;
?  Professor Kenneth Lo Kam-wing, Department of Biology and Chemistry (BCH) & SKLMW;
?  Dr A L Roy Vellaisamy, Department of Physics and Materials Science (AP) & SKLMW;
?  Chair Professor Leung Kwok-wa, EE & SKLMW;
?  Dr Leung Shu-hung, EE & SKLMW;
?  Dr Nelson Chan Sze-chun, EE & SKLMW; 
?  Dr Joshua Lee En-yuan, EE & SKLMW; 
?  Dr Wong Hang, EE & SKLMW;
?  Dr Kim Tae-joon, EE & SKLMW; 
?  Dr Johnny Ho Chung-yin, AP & SKLMW;
?  Dr Lam Yun-wah, BCH & SKLMW;
?  Dr Alex Wong Chun-yuen, BCH & SKLMW.