Environmental Engineering Reference
In-Depth Information
BARNACLE
MUSSEL
PU
PMMA
Figure 4.2
Barnacles attached to PU, polymethyl methacrylate (PMMA) and
mussel surfaces placed in the ocean for one year.
Previous reports show that barnacles (
Chthamalus fragilis
) present on the leaf surfaces
of the plant,
Spartina alternifora
replicate the epithelial cells and the other features
present on the surface of the latter. The barnacle species,
Balanus eburneus
, grows
on vinyl records mainly oriented along the direction of the grooves of the record,
whereas on the smooth side of the record, the barnacles grow in random directions
and not in a ixed pattern. So, it is postulated that the liquid cement secreted by the
barnacles initially completely ills the surface issures of both the base-plate as well
as the substrate. Once solidiied, it ensures a rigid interlocking with the surface. It is
proposed from atomic force microscopy measurements that barnacle cement exists
in layers and the outermost softest cement layer governs the shear strength of the
adhesion. The microstructure of the bulk cement is a function of the supporting
substrate material. Morphological crosslinking is more common in the cement
detached from PMMA when compared to the relatively denser cement detached
from a shell. The porous nature of the cement from the former is relatively absent in
the latter. This suggests that the curing of the cement secreted on the periostracum
(shell) is poorer in comparison to the cement secreted on PMMA or even on metals.
On these materials ibrous or globular microstructures are well-developed. Absence
of any crosslinked structures allow the peeling of the barnacle from the periostracum.
The contact angle measurements suggest that the periostracum is more hydrophilic
than the PMMA surface, but the attachment is stronger on the PMMA.
