A Biosensor may be defined as "a compact analytical device incorporating a biological or biologically-derived sensing element either integrated within or intimately associated with a physico-chemical transducer. The usual aim of a biosensor is to produce either discrete or continuous digital electronic signals which are proportional to a single analyte or a related group of analytes."
Thus Biosensor is an analytical device, which converts a biological response into an electrical signal. The term 'Biosensor' is often used to cover sensor devices used in order to determine the concentration of substances and other parameters of biological interest even where they do not utilize a biological system directly.
A Biosensor is a type of probe in which a biological component such as an enzyme, antibody, or nucleic acid, interacts with an analyte, which is then detected by an electronic component and translated into a measurable electronic signal.
Biosensors come in a large variety of sizes and shapes and are used to monitor changes in environmental conditions. They can detect and measure concentrations of specific bacteria or hazardous chemicals; they can measure acidity levels (pH). In short, biosensors can use bacteria and detect them too.
[...] The micro-organisms were immobilized on a porous acetylcellulose membrane and sandwiched between an oxygen permeable teflon membrane and a porous membrane. Then, the membrane was directly fixed on the surface of the platinum cathode of an oxygen probe. A continuous flow system using a new microbial sensor was developed for automatic estimation of 5 day BOD tests. Furthermore, the BOD of various types of untreated industrial waste water can be estimated by the sensor. The BOD values estimated by the sensor depend upon compounds in the waste water. [...]
[...] Potential Uses in Virtual Reality: Biosensors potentially have a number of uses in the emerging field of Virtual Reality, particularly in the areas of user interaction and the development of these interaction devices. Biosensors could be used as powerful input devices for immersive environments. Imagine a virtual environment in which our entire body was immersed. This environment could react to hand or arm gestures, eye movements, or any muscle or nerve as input. These forms of input are attractive as they are somewhat more natural and intuitive to the user, as the user is accustomed to manipulating the "real" world with such movements. [...]
[...] "Medical telesensor", a chip on a fingertip can measure and transmit body temperature. A chip on your fingertip may someday measure and transmit data on your body temperature. An array of chips attached to your body may provide additional information on blood pressure, oxygen level, and pulse rate. Aging diseases such as diabetes and Alzheimer's, and chemical warfare agents cause changes in metal ion concentrations in the body. These changes can be detected and measured, and the information provide clues about changes in disease states and exposure to toxins. [...]
[...] AMPEROMETRIC BIOSENSORS: Amperometric biosensors function by the production of a current when a potential is applied between two electrodes. They generally have response times, dynamic ranges and sensitivities similar to the potentiometric biosensors. The simplest amperometric biosensors in common usage involve the Clark oxygen electrode. This consists of a platinum cathode at which oxygen is reduced and a silver/silver chloride reference electrode. When a potential of - 0.6 relative to the Ag/AgCl electrode is applied to the platinum cathode, a current proportional to the oxygen concentration is produced. [...]
[...] The frequency of this oscillation depends on their thickness and cut, each crystal having a characteristic resonant frequency. This resonant frequency changes as molecules adsorb or desorb from the surface of the crystal. For any piezo-electric crystal, the change in frequency is proportional to the mass of absorbed material, up to about a change. This frequency change is easily detected by relatively unsophisticated electronic circuits. A simple use of such a transducer is a formaldehyde biosensor, utilizing a formaldehyde dehydrogenase coating immobilized to a quartz crystal and sensitive to gaseous formaldehyde. [...]
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