| Biosensors have been successfully used for water quality screening. However, conventional biosensors have the disadvantage that they often require complicated instrumentation and long analysis time. This research presents proof-of-concept for a novel low-cost, easy-to-use biosensor for the rapid detection of pathogenic bacteria in water using the well-known technology of Radio Frequency (RF)/microwave microstrip bandpass filter circuits. The biosensor is based on a change in response of the bandpass filter when bacteria adhering to the surface of the biosensor cause a change in relative permittivity immediately above the filter. Initial computer simulations and experimental tests using a widely-used filter in microwave engineering, a coupled line bandpass filter, showed that the filter does respond to a dielectric overlay immediately above the filter, but that the sensitivity is low. As determined by further computer simulations, other filter geometries were more sensitive to a dielectric overlay and hence these filters were implemented in the design of the biosensor.; Using an environmental strain of the bacteria Pseudomonas aeruginosa , testing the biosensor was successful, and the measured responses of the biosensor and their analysis are presented. From our results we conclude that highly effective biosensors based on RF microstrip bandpass filter circuits are feasible. Moreover, the fabrication technology for this type of biosensor could be cheap and computer-automated, allowing for the mass production of highly reproducible circuits. |
