Impedance Characteristics of Biofilms Formed on Graphene Films and Their Substrates

Abstract

Biofilms are inhomogeneous film-like matters formed on materials by bacterial activities. They bring about many detrimental problems in various fields such as cooling pipes, kitchens, toilets, baths, marine structures, food industries, medical applications, hospitals etc., as well as beneficial purposes. Therefore, they should be controlled properly and the sensing is very important therefore. We have confirmed so far that graphene as one of representative 2D materials has high sensitivity to biofilm formation due to their pi electron clouds. The characteristics would lead to the application of biofilm sensors. In this experiment, we formed one layer, two layers and multi-layers graphenes were formed by a thermal CVD process on copper substrates and in some cases, they were moved to the surfaces of polyethylene and biofilms were formed on graphene films with those substrates. Then the impedance characteristics were measured and the relation between the impedance characteristics and biofilms formation/growth behaviors were investigated and discussed. As a result, we obtained the following results.1. In the case of graphene films on all substrates, the characteristic peaks of impedance were observed at some specific frequencies.2. The impedance peaks were different between copper substrates and PE ones.3. The impedance peaks were also different according to the numbers of graphene layers.4. The impedance peaks became more remarkable for non-freeze hydrated specimens.5. In the case of polymeric substrates, the impedance characteristics of biofilms showed different patters.We presume that the impedance peaks were obtained, since external polymeric substances (EPS) in biofilms would have absorbed electromagnetic waves. Therefore, the polymeric substrates could have affected the absorbance behaviors of electromagnetic waves differently. The application possibilities of the experimental results to biofilm sensors were finally discussed.