Microfabricated Capacitive Microwave Biosensor for Label-free Escherichia Coli Bacteria Detection

This paper presents a novel label-free microwave biosensor composed of a compact on-silicon capacitor covered with a biofunctionalization layer fabricated with a micrometer range feature size. Selective binding of bacteria is enabled using specific polyclonal anti-Escherichia coli antibodies. Bacteria presence is detected through the change of the mean capacitance value over broad bandwidth related to the post-biofunctionalization state. An experiment was carried out for a set of bacteria with well-established concentrations. The sensor`s measured capacitance was averaged over the 2 - 7 GHz band and the obtained results prove the capability of Escherichia coli detection at concentrations reaching as low as 10(3) CFU/ml. The study results are promising for future biomedical applications, in terms of specific and rapid bacteria detection without the need for their labeling.