Electrochemical[ edit ] Electrochemical biosensors are normally based on enzymatic catalysis of a reaction that produces or consumes electrons such enzymes are rightly called redox enzymes. The sensor substrate usually contains three electrodes ; a reference electrodea working electrode and a counter electrode. The target analyte is involved in the reaction that takes place on the active electrode surface, and the reaction may cause either electron transfer across the double layer producing a current or can contribute to the double layer potential producing a voltage. We can either measure the current rate of flow of electrons is now proportional to the analyte concentration at a fixed potential or the potential can be measured at zero current this gives a logarithmic response.
Biology[ edit ] The variety among biofouling organisms is highly diverse, and extends far beyond the attachment of barnacles and seaweeds. According to some estimates, over 1, species comprising over 4, Soren chemical case solution are responsible for biofouling. Due to the distinct chemistry and biology that determine what prevents them from settling, organisms are also classified as hard- or soft-fouling types.
Calcareous hard fouling organisms include barnaclesencrusting bryozoansmolluskspolychaete and other tube wormsand zebra mussels. Examples of non-calcareous soft fouling organisms are seaweedhydroidsalgae and biofilm "slime". Ecosystem formation[ edit ] Biofouling initial process: Marine fouling is typically described as following four stages of ecosystem development.
The chemistry of biofilm formation describes the initial steps prior to colonization. Within the first minute the van der Waals interaction causes the submerged surface to be covered with a conditioning film of organic polymers.
In the next 24 hours, this layer allows the process of bacterial adhesion to occur, with both diatoms and bacteria e. By the end of the first week, the rich nutrients and ease of attachment into the biofilm allow secondary colonizers of spores of macroalgae e.
Within 2 to 3 weeks, the tertiary colonizers- the macrofoulers- have attached. These include tunicatesmollusks and sessile Cnidarians.
Industrially important impacts are on the maintenance of mariculturemembrane systems e. Biofouling can occur in oil pipelines carrying oils with entrained water, especially those carrying used oils, cutting oilsoils rendered water-soluble through emulsificationand hydraulic oils.
Other mechanisms impacted by biofouling include microelectrochemical drug delivery devices, papermaking and pulp industry machines, underwater instruments, fire protection system piping, and sprinkler system nozzles.
Besides interfering with mechanisms, biofouling also occurs on the surfaces of living marine organisms, when it is known as epibiosis. Medical devices often include fan-cooled heat sinks, to cool their electronic components. While these systems sometimes include HEPA filters to collect microbes, some pathogens do pass through these filters, collect inside the device and are eventually blown out and infect other patients.
Devices used in operating rooms rarely include fans, so as to minimize the chance of transmission. Also, medical equipment, high-end computers, swimming pools, drinking-water systems and other products that utilize liquid lines run the risk of biofouling as biological growth occurs inside them.
Historically, the focus of attention has been the severe impact due to biofouling on the speed of marine vessels. In some instances the hull structure and propulsion systems can become damaged.
Fouling communities may compete with shellfish directly for food resources impede the procurement of food and oxygen by reducing water flow around shellfish, or interfere with the operational opening of their valves .
Consequently, stock affected by biofouling can experience reduced growth, condition and survival, with subsequent negative impacts on farm productivity . Although many methods of removal exist, they often impact the cultured species, sometimes more so than the fouling organisms themselves .
Detection[ edit ] Shipping companies have historically relied on scheduled biofouler removal to keep such accretions to a manageable level. However, the rate of accretion can vary widely between vessels and operating conditions, so predicting acceptable intervals between cleanings is difficult.
LED manufacturers have developed a range of UVC nm equipment that can detect biofouling buildup, and can even prevent it.
Fouling detection relies on the biomass' property of fluorescence. All microorganisms contain natural intracellular fluorophores, which radiate in the UV range when excited. At UV-range wavelengths, such fluorescence arises from three aromatic amino acids - tyrosine, phenylalanine, and tryptophan.
The easiest to detect is tryptophan, which radiates at nm when irradiated at nm. In industrial processesbio-dispersants can be used to control biofouling.
In less controlled environments, organisms are killed or repelled with coatings using biocides, thermal treatments, or pulses of energy. Nontoxic mechanical strategies that prevent organisms from attaching include choosing a material or coating with a slippery surface, creating an ultra-low fouling surface with the use of zwitterionsor creating nanoscale surface topologies similar to the skin of sharks and dolphins, which only offer poor anchor points.
Biocide and Biomimetic antifouling coating Biocides are chemical substances that deter the microorganisms responsible for biofouling.
The chemical substances are incorporated into an anti-fouling surface coating, typically through physical adsorption or through chemical modification of the surface. Biofouling occurs on surfaces after formation of a biofilm. The biofilm creates a surface onto which successively larger microorganisms can attach.
In marine environments this buildup usually concludes with barnacle attachment.Standing prominently above Pasadena, Mount Wilson is a Southern California landmark. The 5, foot summit is home for an observatory responsible for the most detailed photos of Mars as well a vast array of antennae for local LA radio and television stations.
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