Biofilm Formation on Two Layer CVD Graphene and Its Change of Capacitance

Abstract

Biofilms formed on materials have brought about many industrial problems so far. Chronic diseases, the deterioration of hygiene conditions etc. could be mentioned for example. We have confirmed that graphene is easy to form biofilms on it in various ways. Therefore, we expect and predict it could be applied to a practical sensor for biofilm detections. In our precious studies, we produced mono layer graphene on glass specimens and confirmed that it was highly sensitive to biofilm formation in a flow type laboratory biofilm reactor. However, monolayer graphene is generally still lacking in uniformity and the non-coating area is often observed. Therefore, we investigated the sensitivity of two layer CVD graphene to biofilm formation and the possibility to biofilm sensor.In this study, we focused on the change of capacitance with biofilm formation on the graphene coating. The graphene coating specimens on copper and PET substrates were set to laboratory biofilm reactors and we formed biofilms on the specimens artificially. After the formation of biofilms, the specimens were checked by Raman spectroscopy and also observed by an optical microscopy. And the specimens' capacitances were measured, using a specially devised jig connecting to a LCR meter. The frequencies were changed from 700 to 2000Hz and the capacitances were measured.As a result, biofilm formed specimens showed small peaks at some characteristics frequencies, while specimens without biofilms showed no peaks at all. Therefore, we presumed that dielectric polarization-relaxation and the loss would occur due to the existence of External Polymeric Substances (EPS) derived from biofilms. We discussed the application possibility of this phenomenon to biofilm sensing.