Bacterial biofilm detection using a fiber optic Mach-Zehnder interferometer

In this work, we report about the detection of biofilm growth formation using fiber optic sensing technology. The optical configuration involved a fiber optic tip integrating a Mach-Zehnder interferometer (MZI). The simple and cost-effective fabricating process employs standard single-mode fiber SMF28, a splice with overlap as coupling/re-coupling element for the fiber modes, and a silver mirror enabling a reflective configuration to have a miniaturized and compact device. As a case study, the growth of bacterial biofilm of <i>Pseudomonas alcaligenes</i> was monitored in real-time during about 60 hours by observing the resonance wavelength shift of the MZI. The biofilm layer formation was further confirmed by Atomic Force Microscopy analysis and its thickness measured. These findings pave the way for the development of highly sensitive miniaturized probes for the detection of different types of biofilms, to be applied in a wide range of domains, from biomedical to industrial fields as well as environmental monitoring.