Marine biofilm sensor

Materials World magazine
,
1 Aug 2009

An electrochemical device has been developed to detect bacterialbiofilm formation on metals exposed to seawater. Scientists at theUniversity of Southampton, UK. hope to adapt their system formonitoring marine seawater pipes and aimto identify natural biocides that can destroy biofilms, replacing thetoxic chemicals currently used.

Biofouling occurs when bacterial biofilms adhere to exposed metallic surfaces, such as titanium or copper alloys.

Their development can reduce the operational performance of marine heat exchangers inside the vessels, as well as damage fluid-handling components, leading to frequent failures.

Such films have proved difficult to monitor due to their complex nature and the lack of understanding of biofouling formation on metals.

Now, researchers at the National Centre for Advanced Tribology at Southampton have developed devices with a gold sensing area that can detect the presence of biofilms and their initial evolution over three days, which is the typical lifespan of the bacteria used in the study.

‘The sensor measures the impedance at the bulk solution (seawater)/gold interface,’ explains Stéphane Werwinski, who is carrying out the research as part of a PhD project sponsored by the UK Ministry of Defence and the Engineering and Physical Sciences Research Council. ‘When a biofilm forms on the sensing area, there is a change in the electrochemical properties at the interface, thus affecting interfacial impedance.’

To verify exactly what is being detected, Werwinski and colleagues have run trials of the sensor in solutions with different biochemical characteristics, including low laminar flows and controlled room temperature, using a single bacterial species.

This allows bacterial biofilms to be ‘uniquely studied’ in a specific environment.

‘The idea is to define biofouling indicators using the sensing response by looking at informative changes in impedance over time due to the presence of biofilms,’ explains Werwinski. So far, results from the device have been corroborated by a series of electrochemical methods and fluorescence microscopy.

Understanding of the initial bacterial colonisation, and its extent of growth, will allow the sensor to be adapted to detect film growth in specific locations (for example, by compensating for different pH and dissolved oxygen levels, as well as conductivity capabilities).

Methods of ‘disrupting’ the biofilms are also under investigation by dosing biofilmed surfaces with different biocides using a flow cell system at the National Oceanography Centre at Southampton. ‘An attractive and alternative option, to meet increasing ecological concerns, would be to establish an effective and efficient natural biocide strategy,’ says Werwinski.