• Wharton, Julian A.
• Salta, Maria
• Stokes, Keith R.
• Carugo, Dario
• Capretto, Lorenzo

Abstract

Marine biofouling is the accumulation of organisms on underwater surfaces, causing increased hydrodynamic drag, resulting in higher fuel consumption and decreased speed and range. Biofilms constitute a major component of the overall biofouling, for example, fuel penalties from increased surface roughness due to biofilms (5 μm – 1 mm) are commonly reported (e.g. Schultz, 2007). Recent commercial antifouling technologies have managed to significantly reduce the effect of macrofoulers, however, marine biofilms are still an issue as they are known to remain attached even at high ship speeds (30-50 knots; Townsin and Anderson, 2009). The majority of reported biofilm studies involve the use of macro-scale reactors. However, more recently, there has been increased awareness that microfluidic systems provide several advantages, including inexpensive fabrication, highly parallel throughput, small size, and greater control over the microenvironment for cell culture (Meyer et al. 2011).<br/><br/>For this reason, we have developed and fabricated a novel lab-on-a-chip device for the investigation of the biofilm response to different hydrodynamic conditions. The microfluidic flow channel is designed using computational fluid dynamic simulations so as to have a pre-defined, homogeneous wall shear stress in the channels, ranging from 0.07 to 4.5 Pa, which are relevant to in-service conditions on a ship hull. The applicability of this approach has been demonstrated using a selected natural product (juglone - 5-hydroxy-1,4-naphthalenedione), which has previously been shown to have antifouling efficacy in static bioassays, where it allowed the investigation of the simultaneous effect of wall-shear stress and the natural product on biofilm structure. The results allowed for the first time the direct observation of the natural product influence on newly attached marine biofilms and the evolution of the antifouling effect with time. Biofilm attachment behaviour appeared to be markedly different in the presence of the natural product, illustrated by limited cluster and extracellular polymeric substance formation which suggests an interference of the bacterial attachment mechanisms.

Topics

• impedance spectroscopy
• surface
• cluster
• simulation