On-chip impedance measurements to monitor biofilm formation in the drinking water distribution network

Aquatic microorganisms have the ability to adhere onto any solid surface. They are able to re-organise as biofilms when environmental conditions change and put their life at risk. Biofilms allow bacteria to remain inside water pipes without being eliminated by biocides. Among other properties, biofilms are electrically insulating. Because of this, as they grow on a metal transducer surface, biofilms produce changes in the electrode-solution interface properties. These changes have been monitored using impedance measurements and microchips as electrical transducers. Biofilm formation has been characterised using on-chip gold working electrodes and the various growth phases have been related to specific impedance changes. Measurements employing new and reused chips of bacterial and non-bacterial solutions have been performed. Although differences between new and reused chips have been found, both kinds of electrodes can be used to evaluate biofilm formation. The effect of several biocides on biofilms has also been studied. The disinfecting properties of peroxides, strong acid/bases and alcohols have been compared as well as their ability to remove adhered substances from chip surfaces. © 2006 Elsevier B.V. All rights reserved.