| To understand the problem of biofouling, a model system has been developed to investigate the role of shear-induced fracture of rigid objects (i.e. biofoulings) adhered to thin soft material. A model has been proposed and experimentally verified. The tangential shear force required to fracture can be described by the relation, s*s∼a/ℓ Wam/h . The critical shear stress (sigma* s), defined as the stress where the rigid object separates from a thin elastomeric film, increases with the modulus (mu) of the film, but decreases with the thickness (h) following a square root relationship. The critical stress for shear fracture (sigma* s) also depends on the external length scales, i.e. the length of the prism (a) and the plane of the application of shear stress (ℓ). A separate study to understand the role of interfacial interaction ( Wa) was also conducted. The effect of the interfacial interaction was investigated by the application of additional polar interaction (i.e. hydrogen bonding). The non-polar interaction ( i.e. Van der Waals interaction) was achieved by silanization of the rigid object by methyl terminated silanes but the polar interaction was incorporated by the application of polyelectrolyte multilayers (PEM). It is found that the thermodynamic work of adhesion (Wa) increases in the presence of the additional polar interaction at the interface. The analytic model for critical shear stress is still valid for both cases. The shear fracture takes places at the polyelectrolyte/elastomer interface via breaking of the hydrogen bonds, verified from the results of AFM and XPS analysis. Experiments have been conducted to investigate the stability of the adhered interfaces under water. It was found that critical shear stresses at the polyelectrolyte/elastomer interface in the aqueous environment were lower than those at the interface in air.;It is found that the silanized glass prism continues to slide on the elastomeric film as long as the applied shear stress is less than a critical value. During this sliding process, an elastic instability has been developed at the interface that resulted in the formation of numerous bubbles. The lateral dimension of these bubbles was found to be comparable to the thickness of the film, and their speed to be 1000 times faster than the overall sliding speed of the object against the thin elastomeric film. |
