RF MEMS-Based Biosensor for Pathogenic Bacteria Detection

Abstract

A biosensor which is used for determining the concentration of substances and other parameters of biological interest is an integral part of the public health systems. Micromachined sensors based on radio frequency–microelectromechanical systems are an emerging field of study for biosensing applications. In this work, we propose a novel detection method for pathogenic bacteria using a coplanar waveguide (CPW) as well as distributed microelectromechanical systems transmission line (DMTL). Escherichia coli has been chosen for the study due to the widespread food poisoning outbreaks caused by its infective strains. But, the model can be easily extended to other pathogenic bacteria as well. The E. coli bacterium was modeled as a three-shell structure based on the electrical properties of the E. coli cell. An initial study was done using a CPW. The scattering parameters and voltage standing wave ratio were analyzed and found to vary as the number of bacteria positioned on the CPW increased. Reflection parameters were found to have more deviation than the transmission parameters. DMTL was designed by introducing periodic structures in CPW, to allow increased interaction between the electromagnetic waves and the measurand. This improved the quality factor of the resonant peaks in reflection coefficient, thereby allowing us to correlate the number of bacteria to the shift in resonant frequency. Selectivity towards E. coli bacteria can be achieved by immobilizing a functionalization layer of anti E. coli antibody on the central conductor of CPW/DMTL. With sufficient calibration, this method can be used to detect and measure the concentration of other pathogenic bacteria as well.