The adhesion of the barnacle, Balanus improvisus, to poly(dimethylsiloxane) fouling-release coatings and poly(methyl methacrylate) panels: The effectof barnacle size on strength and failure mode

Measure men ts were made of the bond strength of cyprids and barnacles (Bal anus improvisus) attached to poly(dimethylsiloxane) (PDMS) fouling-release coatings and poly(methyl methacrylate) (PMMA) panels as a function of barna cle base plate size (0.05-90 mm(2)). The vertical forces necessary to dislo dge cyprids and newly metamorphosed barnacles (base plate < 0.5 mm(2)) 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 barn acles (base plate > 0.5 mm(2)) 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 barnacl e growth. This transition. which is a measure of the balance between the co hesive strength of the barnacle base plate and the adhesion bond to the sur face, occurs earlier or with smaller barnacles when detached from the PDMS. The quantification of the remaining fraction of the base plate at the poly meric failure surfaces appears to be a function of barnacle bioadhesive bon d strength and is, therefore, suggested to be used as a new parameter for e valuating the release properties of new coatings formulations.