Tag: Biomedical sensors
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Polarizable vs. Non-Polarizable Electrodes
We may categorize electrodes into two possible types albeit theoretically: those that are perfectly polarizable and those that are perfectly non-polarizable. This categorization is based on what happens to an electrode when a current passes between it and the electrolyte. Perfectly polarizable electrodes are those in which no actual charge crosses the electrode-electrolyte interface when…
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The Principle of Immunoassay Biosensor
The principle of immunoassay sensor operation is based on the observation of ligand-binding reaction products between a target analyte and a highly specific binding reagent. The important component of an immunosensor is the biological recognition element, which normally consists of antibodies or antibody fragments. Immunological methods offer remarkable selectivity and sensitivity through the process of…
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Basic Features of Intravascular Fiber Optic Blood Gas Sensor
Intra-arterial blood gas sensors usually use a single or double fiber configuration. Typically, the matrix containing the indicator is attached to the end of the optical fiber. Because the solubility of O2 and CO2 gases, as well as the optical properties of the sensing chemistry itself, is affected by the temperature variations, fiber optic intravascular…
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Commonly used EEG Electrodes
The most commonly employed electrodes for recording electroencephalographic signals from the brain (EEG) are cup electrodes and subdermal needle electrodes. Cup electrodes are fabricated from platinum or tin approximately 5-10 mm in diameter. These cup electrodes are filled with a conducting electrolyte gel and can be attached to the scalp with adhesive tape. Recording of…
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The Principles of Microbial Biosensors
Introduction The underlying basis of a microbial biosensor is the close proximity between an immobilized microorganism that serves as a specific recognition element and an electrochemical or optical sensing transducer that is used to convert the biochemical signal into an electronic signal that can be processed. The manufacture of a microbial biosensor requires the immobilization…
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The Operation of Fiber-optic Based Blood Gas Sensors
To perform in vivo measurements and to steadfastly analyze blood gases, a small, stable, accurate and bio-compatible sensor is needed that can be inserted in the blood flow of an artery through an arterial cannula and remain in place for several days. Additional, it has to be low cost so that it could be used…
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The Principle of Surface Plasmon Resonance Sensors for Detection of Antibody & Antigen Interactions
When monochromatic polarized light for instance, from a laser source impinges on a transparent medium having a conducting metallized surface (e.g. Ag or Au), there is a charge density oscillation at the interface. When a light at an appropriate wavelength interacts with the dielectric-metal interface at a defined angle, called the resonance angle, there is…
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The Principle of Temporal Artery Thermometer
This is a non-invasive scanning thermometer for measuring core body temperature. The measurement is based on scanning the area above the temporal artery using an IR detector. The superficial temporal artery extends directly from the external carotid artery and travels in front of the ear. Anatomically, it is lying approximately 1 mm below the skin,…
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Basic Features of Enzyme Based Biosensors
Enzymes are the commonly used biological sensing element in the fabrication of various biosensors. Enzymes have unique properties and ability to accelerate chemical reactions inside biological cells. Most enzymes react only with specific substrates even though they may be contained in a complicated mixture with other substances. However, it is imperative to keep in mind,…