A research paper titled “Highly Efficient Cash Sterilization with Ultrafast and Flexible Joule-Heating Strategy by Laser Patterning” by Prof. Mitch LI (Assistant Professor, Division of Integrative Systems & Design) and his research team, in collaboration with University of Strathclyde, was recently published on Advanced Materials Interfaces, an interdisciplinary journal focusing on applied surface and interface-related research blending of physics, chemistry, materials science, and life science. 

Cash remains a widely used medium of exchange in many societies, but its frequent circulation among numerous individuals increases the risk of pathogen spread. Current disinfection techniques, such as chemical treatments or ultraviolet (UV) radiation, often fall short in providing rapid and thorough sterilization of banknotes in an efficient manner.

To address the potential risks associated with pathogen transmission through banknotes, the HKUST research team consisting of Prof. Mitch LI and his research postgraduate students from Division of Integrative Systems & Design, introduces an ultrafast Joule-heating device created through laser patterning, which can be widely employed in sterilizing banknotes and various objects, safeguarding the public from bacterial contamination in daily life.

This newly developed method for fabricating an ultrafast Joule-heating device uses laser patterning on a copper-cladded polyimide film. This approach enables fast and scalable production of flexible heaters. The thin heater film is highly flexible, capable of bending up to 180 degrees. By integrating patterned copper wires designed to create a uniform temperature distribution, in conjunction with a Proportional – Integral – Derivative(PID)-controlled Printed Circuit Board (PCB), the device achieves rapid and precise heating. Through extensive testing, the researchers found that their Joule-heating device efficiently sterilizes common bacteria, including E. coli and S. aureus, within a mere 30 seconds, at a heating temperature of 90°C. 

The impact of this breakthrough technology on the public is substantial. The ultrafast flexible Joule heater can be conveniently incorporated into wallets, making it effortless for individuals to use when handling cash received from others. The entire sterilization process takes just half a minute, causing no significant disruption to the normal use of banknotes. By employing this device, individuals can ensure that the cash in their wallets remains disinfected, effectively reducing the potential transmission of pathogens through currency and contributing to the prevention of pandemics.