Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 7 de 7
Filter
Add more filters










Database
Language
Publication year range
1.
Biofouling ; 32(4): 451-64, 2016.
Article in English | MEDLINE | ID: mdl-26958740

ABSTRACT

A test coupon coated with light calcareous tubeworm fouling was scanned, scaled and reproduced for wind-tunnel testing to determine the equivalent sand grain roughness ks. It was found that this surface had a ks = 0.325 mm, substantially less than the previously reported values for light calcareous fouling. This result was used to predict the drag on a fouled full scale ship. To achieve this, a modified method for predicting the total drag of a spatially developing turbulent boundary layer (TBL), such as that on the hull of a ship, is presented. The method numerically integrates the skin friction over the length of the boundary layer, assuming an analytical form for the mean velocity profile of the TBL. The velocity profile contains the roughness (fouling) information, such that the prediction requires only an input of ks, the free-stream velocity (ship speed), the kinematic viscosity and the length of the boundary layer (the hull length). Using the equivalent sandgrain roughness height determined from experiments, a FFG-7 Oliver Perry class frigate is predicted to experience a 23% increase in total resistance at cruise, if its hull is coated in light calcareous tubeworm fouling. A similarly fouled very large crude carrier would experience a 34% increase in total resistance at cruise.


Subject(s)
Biofilms/growth & development , Biofouling/prevention & control , Polychaeta/growth & development , Ships , Animals , Friction , Mechanics , Risk Assessment/methods , Ships/methods , Ships/standards , Surface Properties , Total Quality Management/methods
2.
Biofouling ; 29(2): 195-202, 2013.
Article in English | MEDLINE | ID: mdl-23330727

ABSTRACT

The use of vibration is proposed as a means of controlling the settlement of marine fouling organisms. In this study, panels with embedded lead zirconate titanate, known as PZT, were placed in the field over 3 months. The panels were vibrated at different velocity levels at frequencies between 70 and 445 Hz. It was found that barnacles (Amphibalanus variegatus Darwin and Elminius sp.) were the only fouling organisms affected by the applied vibration, and these organisms settled in significantly lower numbers when the plates were excited at specific frequencies and amplitudes. Panels vibrating at relatively higher frequencies, greater than 260 Hz, exhibited reduced barnacle settlement, whilst lower frequencies in the 70-100 Hz range had little or no effect. The settlement of other fouling organisms such as tubeworms, bryozoans, ascidians and algae did not appear to be affected by the applied excitation. The experimental results showed that increasing the velocity amplitude of vibration was a contributing factor in inhibiting barnacle settlement.


Subject(s)
Biofouling/prevention & control , Lead/chemistry , Thoracica/physiology , Titanium/chemistry , Vibration , Zirconium/chemistry , Acrylates/chemistry , Animals , Cestoda/physiology , Computer Simulation , Lasers, Gas , Marine Biology/methods , Population Density , Species Specificity , Thoracica/chemistry , Time Factors , Urochordata/physiology
3.
Biofouling ; 26(3): 367-77, 2010 Apr.
Article in English | MEDLINE | ID: mdl-20169477

ABSTRACT

Prevention of epibiosis is of vital importance for most aquatic organisms, which can have consequences for their ability to invade new areas. Surface microtopography of the shell periostracum has been shown to have antifouling properties for mytilid mussels, and the topography shows regional differences. This article examines whether an optimal shell design exists and evaluates the degree to which shell microstructure is matched with the properties of the local fouling community. Biomimics of four mytilid species from different regional provenances were exposed at eight different sites in both northern and southern hemispheres. Tendencies of the microtopography to both inhibit and facilitate fouling were detected after 3 and 6 weeks of immersion. However, on a global scale, all microtopographies failed to prevent fouling in a consistent manner when exposed to various fouling communities and when decoupled from other shell properties. It is therefore suggested that the recently discovered chemical anti-microfouling properties of the periostracum complement the anti-macrofouling defence offered by shell microtopography.


Subject(s)
Animal Shells/anatomy & histology , Biofilms , Mytilus edulis/anatomy & histology , Animal Shells/microbiology , Animals , Mytilus edulis/microbiology
4.
Biofouling ; 25(1): 83-93, 2009.
Article in English | MEDLINE | ID: mdl-18985468

ABSTRACT

Material science provides a direct route to developing a new generation of non-toxic, surface effect-based antifouling technologies with applications ranging from biomedical science to marine transport. The surface topography of materials directly affects fouling resistance and fouling removal, the two key mechanisms for antifouling technologies. However, the field is hindered by the lack of quantified surface characteristics to guide the development of new antifouling materials. Using a biomimetic approach, key surface parameters are defined and quantified and correlated with fouling resistance and fouling removal from the shells of marine molluscs. Laser scanning confocal microscopy was used to acquire images for quantitative surface characterisation using three-dimensional surface parameters, and field assays correlated these with fouling resistance and fouling release. Principle component analysis produced a major component (explaining 54% of total variation between shell surfaces) that correlated with fouling resistance. The five surface parameters positively correlated to increased fouling resistance were, in order of importance, low fractal dimension, high skewness of both the roughness and waviness profiles, higher values of isotropy and lower values of mean surface roughness. The second component (accounting for 20% of variation between shells) positively correlated to fouling release, for which higher values of mean waviness almost exclusively dictated this relationship. This study provides quantified surface parameters to guide the development of new materials with surface properties that confer fouling resistance and release.


Subject(s)
Annelida/growth & development , Biomimetics , Chlorophyta/growth & development , Mollusca/chemistry , Mollusca/classification , Urochordata/growth & development , Animals , Bivalvia/chemistry , Bivalvia/classification , Bivalvia/ultrastructure , Gastropoda/chemistry , Gastropoda/classification , Gastropoda/ultrastructure , Marine Biology , Microscopy, Confocal , Mollusca/ultrastructure , Species Specificity , Surface Properties
5.
Biofouling ; 25(8): 757-67, 2009 Nov.
Article in English | MEDLINE | ID: mdl-20183134

ABSTRACT

Nano-engineered superhydrophobic surfaces have been investigated for potential fouling resistance properties. Integrating hydrophobic materials with nanoscale roughness generates surfaces with superhydrophobicity that have water contact angles (theta) >150 degrees and concomitant low hysteresis (<10 degrees ). Three superhydrophobic coatings (SHCs) differing in their chemical composition and architecture were tested against major fouling species (Amphora sp., Ulva rigida, Polysiphonia sphaerocarpa, Bugula neritina, Amphibalanus amphitrite) in settlement assays. The SHC which had nanoscale roughness alone (SHC 3) deterred the settlement of all the tested fouling organisms, compared to selective settlement on the SHCs with nano- and micro-scale architectures. The presence of air incursions or nanobubbles at the interface of the SHCs when immersed was characterized using small angle X-ray scattering, a technique sensitive to local changes in electron density contrast resulting from partial or complete wetting of a rough interface. The coating with broad spectrum antifouling properties (SHC 3) had a noticeably larger amount of unwetted interface when immersed, likely due to the comparatively high work of adhesion (60.77 mJ m(-2) for SHC 3 compared to 5.78 mJ m(-2) for the other two SHCs) required for creating solid/liquid interface from the solid/vapour interface. This is the first example of a non-toxic, fouling resistant surface against a broad spectrum of fouling organisms ranging from plant cells and non-motile spores, to complex invertebrate larvae with highly selective sensory mechanisms. The only physical property differentiating the immersed surfaces is the nano-architectured roughness which supports longer standing air incursions providing a novel non-toxic broad spectrum mechanism for the prevention of biofouling.


Subject(s)
Biofouling/prevention & control , Materials Testing , Polymers/pharmacology , Siloxanes/pharmacology , Animals , Bryozoa/drug effects , Bryozoa/growth & development , Diatoms/drug effects , Diatoms/growth & development , Hydrophobic and Hydrophilic Interactions , Marine Biology , Nanostructures , Polymers/chemistry , Siloxanes/chemistry , Surface Properties , Thoracica/drug effects , Thoracica/growth & development , Ulva/drug effects , Ulva/growth & development
6.
Biofouling ; 24(1): 45-53, 2008.
Article in English | MEDLINE | ID: mdl-18066730

ABSTRACT

This paper examines attachment point theory in detail by testing the fouling attachment of several fouling groups to a microtextured matrix. Static bioassays were conducted on polycarbonate plates with nine equal regions, comprising eight scales of microtexture (4-512 microm) and one untextured region. The microtextures examined were continuous sinusoidal ridges and troughs of defined height and width. Attachment over the microtextured plates was examined for the diatom Amphora sp., the green alga Ulva rigida, the red alga Centroceras clavulatum, the serpulid tube worm Hydroides elegans and the bryozoan Bugula neritina. It was found that the size of the microtexture in relation to the size of the settling propagules/larvae was important in the selection of attachment sites. Attachment was generally lower when the microtexture wavelength was slightly smaller than the width of the settling propagules/larvae and increased when the wavelength was wider than their width. The effect of attachment points was weak for small motile microfoulers (Amphora sp. and U. rigida) (7 microm), strong for large macrofouling larvae (H. elegans and B. neritina) (129-321 microm) and non-existent for the non-motile algal spores (C. clavulatum) (37 microm). This study reinforces the potential of using attachment points to develop surfaces with increased fouling resistance or, alternatively, surfaces which promote the attachment of selected target sizes of motile propagules or larvae.


Subject(s)
Bryozoa/physiology , Diatoms/growth & development , Polycarboxylate Cement/pharmacology , Polychaeta/growth & development , Rhodophyta/growth & development , Ulva/growth & development , Adhesiveness , Animals , Cell Size , Larva/physiology , Metamorphosis, Biological/drug effects , Spores/physiology , Surface Properties , Wettability
7.
Biofouling ; 22(1-2): 55-60, 2006.
Article in English | MEDLINE | ID: mdl-16551561

ABSTRACT

This paper explores diatom attachment to a range of laser etched polyimide surfaces to directly test 'attachment point theory'. Static bioassays were conducted on microtextured polyimide surfaces using four diatom species, Fallacia carpentariae, Nitzschia cf. paleacea, Amphora sp. and Navicula jeffreyi with cell sizes ranging from 1-14 microm. The microtextured polyimides were modelled from natural fouling resistant bivalve surfaces and had wavelengths above, below and at the same scale as the diatom cell sizes. Diatoms attached in significantly higher numbers to treatments where the numbers of attachment points was highest. The lowest diatom attachment occurred where cells were slightly larger than the microtexture wavelength, resulting in only two theoretical points of attachment. The results support attachment point theory and highlight the need to address larval/cell size in relation to the number of attachment points on a surface. Further studies examining a range of microtexture scales are needed to apply attachment point theory to a suite of fouling organisms and to develop structured surfaces to control the attachment and development of fouling communities.


Subject(s)
Biomimetic Materials/chemistry , Diatoms/cytology , Resins, Synthetic/chemistry , Cell Adhesion , Cell Size , Microscopy, Electron, Scanning
SELECTION OF CITATIONS
SEARCH DETAIL