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Abstract
Measurements were made of the bond strength of cyprids and barnacles (Balanus improvisus) attached to poly(dimethylsiloxane) (PDMS) fouling-release coatings and poly(methyl methacrylate) (PMMA) panels as a function of barnacle base plate size (0.05-90 mm2). The vertical forces necessary to dislodge cyprids and newly metamorphosed barnacles (base plate < 0.5 mm2) were found to be equal for the two different substrates. This unexpected result was explained by the occurrence of cohesive failure in the cyprid/barnacle part. A significantly higher detachment force was observed for larger barnacles (base plate > 0.5 mm2) when dislodged from the PMMA compared to the PDMS. Analysis of the failure surfaces with light microscopy and scanning electron microscopy (SEM) showed a gradual transition in failure mode from a total cohesive within the barnacle to a mixed failure mode during barnacle growth. This transition, which is a measure of the balance between the cohesive strength of the barnacle base plate and the adhesion bond to the surface, occurs earlier or with smaller barnacles when detached from the PDMS. The quantification of the remaining fraction of the base plate at the polymeric failure surfaces appears to be a function of barnacle bioadhesive bond strength and is, therefore, suggested to be used as a new parameter for evaluating the release properties of new coatings formulations.
