HKUST Develops More Efficient Disinfection Method with Ultraviolet LED



Researchers at the Hong Kong University of Science and Technology (HKUST) have discovered a novel way to enhance the efficiency of the ultraviolet (UVC) light-emitting diode (LED) disinfection technique, and developed a closet that could kill 99.99% of the bacteria and viruses on the garment inside within a minute. The closet is now in use at three special schools under Po Leung Kuk.


Prof. Ricky LEE Shi-Wei (middle), Chair Professor of the Department of Mechanical and Aerospace Engineering at HKUST demonstrates how the UVC LED disinfection closet works,
along with Mr. LAM Kwok Wai (left) and Mr. Martin MAK, Principal and Assistant Warden respectively of the Po Leung Kuk Yu Lee Mo Fan Memorial School.


UVC is widely used for disinfecting purposes in private and public facilities, but the light source of existing UVC disinfection products are mainly mercury lamps, which not only has lower germicidal efficiency, but is also bulkier with a much shorter lifespan than the LED light .  Moreover, mercury lamp has a longer disinfection cycle and requires time for warming up while LED emits light instantly.  Since last year, over 140 nations, including US, EU, China, Japan and Australia, have implemented a treaty on gradually phasing out the use of toxic mercury in commercial and industrial processes.


Comparison of the efficiency between mercury lamp and UVC LED.


However, despite LED light’s superiority over its mercury-based counterpart, it is not yet widely adopted in sterilization products due to its narrow beam angle and low output efficiency with traditional single-layer reflector. Now, Prof. Ricky LEE Shi-Wei, Chair Professor of the Department of Mechanical and Aerospace Engineering and Director of the Electronic Packaging Laboratory at HKUST, offered a solution with the stacked silicon reflector developed by his team. Through its unique structure and optical design, this new reflector has not only nearly doubled the UVC output efficiency from 50% to over 90%, but has also extended the sterilization distance by more than 5 times to 26cm, while simultaneously achieving uniform radiation.


Funded by the Innovation and Technology Commission under the Public Sector Trial Scheme for Coronavirus Disease 2019, HKUST has built a disinfection closet using this new UVC LED packaging technology. In collaboration with Po Leung Kuk, the closet is now being trialed in three of its special schools.


The closet is now being trialled in three of Po Leung Kuk special schools - including Po Leung Kuk Mr. & Mrs. Chan Pak Keung Tsing Yi School (as pictured above).


Mr. LAM Kwok Wai, Principal of Po Leung Kuk Yu Lee Mo Fan Memorial School which has participated in the scheme, said Po Leung Kuk was very pleased about this collaboration. “The closet is an effective tool which not only greatly enhances disinfection efficiency, reduces our staff’s workloads, but also safeguards the health and safety of our staff and students during the pandemic. Prof Lee’s team has been very attentive to our practical needs since the design stage and has added partitions to the closet so that garments, students’ items and toys can be sanitized simultaneously in just one minute,” he said, adding that Po Leung Kuk expects the continued partnership by extending this innovative technology to other dormitories and service units under the group, so as to benefit more people in need.


Prof. Lee said, "We are happy to see that our research work can help make an impact on people’s daily lives. We will continue to explore new areas of applications for our technology, such as self-cleansing air purifiers and air conditioners, water dispensers or sweeping robots. We look forward to more collaborations with the industry on developing larger scale UVC LED products."


Apart from garments, students` items and toys can also be sanitized in the closet.


Prof. Lee is a world renowned expert in electronics and LED packaging. He has dedicated his career to advancing microelectronics and optoelectronic devices such as LED lights. In 2009, the MTR replaced its train carriage lighting system with the High Brightness Light Emitting Diode (HD-LED) Solid State Lighting (SSL) modules developed by Prof. Lee and his team, which was widely recognized for its benefits over traditional fluorescent tubes in terms of energy and cost efficiency as well as environmental friendliness.