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Monir Alrashid Hadya Mahmoud 20144018 Sandra dashan 20155872 Hadya Mahmoud 20144018 Sandra dashan 20135262 Lael rouhafzay 20155740 Aya chebib 20144861 Leila karimizarandi 20165555 Moath helal 20164946 Nuhu Abdulhaqq Isa 20122792 Biomedical Engineer Biosensor BME301 2016-2017

))))))) Introduction Definition Types Conclusion

Chemical sensors are very different & quite common ))))))) Introduction Chemical sensors are very different & quite common Sensing is usually based on sampling Sample is allowed to react in some fashion with elements of the sensor Usually an electric output is produced Transduction can be multi-stage and complex In some sensors, a complete analysis of the substance occurs In others a direct output occurs simply due to the presence of the substance.

Used in industry for process control and for monitoring for safety. ))))))) Introduction Used in industry for process control and for monitoring for safety. Important role in environmental protection Tracking of hazardous materials Tracking natural and man made occurrences pollution waterways infestation migration of species weather prediction and tracking.

In sciences and in medicine - sampling of substances such as: ))))))) Introduction In sciences and in medicine - sampling of substances such as: oxygen, blood, alcohol In the food industry for monitoring food safety Military has been using chemical sensors at least since WWI to track chemical agents used in chemical warfare Around the home and for hobbies (CO detection, smoke alarms, pH meters)

Electrical output signal Molecular recognition ))))))) Definition Chemical input Sample Free particle Electrical output signal Bound Particle Analytical result Electronic Transducer Signal wave Molecular recognition lllllllllllllllllllllllllllllllllllllllllllllllll l Heat Electron Masses Light …

))))))) Definition A chemical sensor is an analytical device that transforms chemical information (composition, presence of a particular element or ion, concentration, chemical activity, partial pressure…) into a useful signal. Chemical sensor is an inexpensive, portable, foolproof device that responds with perfect and instantaneous selectivity to a particular target chemical substance (analyte) present in any desired medium in order to produce a measurable signal output at any required analyte concentration. Chemical sensors in actuality are complex devices, generally optimized for a particular application.

))))))) Definition The complexity of a chemical sensor application is related to the technical difficulties associated with these determinations and with the specific nature (i.e., elemental or molecular) of the chemical substance to be analyzed. Given the huge number (>106) of known molecular substances, molecular sensing typically relies on recognition of molecular structure or associated reactivity; this recognition aspect is called selectivity. Sensitivity and limit of detection relate to the quantity or concentration of the element or molecule to be analyzed (the analyte). The quantity of analyte present in a sample can have a dynamic range of greater than 1023, and chemical sensors are commonly required to detect 10-9 molar concentrations or less.

))))))) Definition The sensitivity and selectivity aspects of chemical sensing are affected by the phase, dimensional, and temporal aspects of the desired determination. The analyte can be present in a gas, liquid, or solid phase on various dimensional scales ranging from bulk volumes of liters to picoliters, or surface layers from nanoscopic to monomolecular scale. It may also be persistent or transitory. Finally, economic resources and constraints can affect the design and strategy of any sensing task in many different ways.

))))))) Types The chemical reaction or the presence of a chemical produces a measured electrical output. Direct output Indirect (also called complex) sensor relies on a secondary, indirect reading of the sensed stimulus. Indirect

))))))) Types The capacitive moisture sensor – the capacitance of a capacitor is directly proportional to the amount of water present between its plates. Direct output Optical smoke detector. An optical sensor such as a photoresistor is illuminated by a source and establishes a background reading. Some chemical sensors are much more complex than this and may involve more transduction steps. Indirect

))))))) Types Direct output Indirect

selectivity; characteristics sensitivity; limit of detection; ))))))) Types characteristics selectivity; sensitivity; limit of detection; response time; Packaging size;

SENSORS WITH SAMPLE SEPARATION ))))))) Types Optical sensors: Transform changes of optical phenomena, which are the result of an interaction of the analyte with the receptor part. It applies to optical properties such as absorbance, reflectance, luminescence, fluorescence, refractive index etc. Electrochemical sensors: Transform the effect of the electrochemical interaction analyte - electrode into a useful signal. Such effects may be stimulated electrically or may result in a spontaneous interaction. Examples are voltametric, potentiometric, chemically sensitized field effect transistor (CHEMFET), potentiometric solid electrolyte gas sensors. SENSORS WITH SAMPLE SEPARATION

SENSORS WITH SAMPLE SEPARATION ))))))) Types Electrical devices based on measurements, where no electrochemical processes take place, but the signal arises from the change of electrical properties caused by the interaction of the analyte. Examples are, metal oxide sensors, organic semiconductor sensors, electrolytic semiconductor sensors, etc. Mass sensitive devices transform the mass change at a specially modified surface into a change of a property of the support material. The mass change is caused by accumulation of the analyte. Examples are piezoelectric devices and surface acoustic devices. SENSORS WITH SAMPLE SEPARATION

SENSORS WITH SAMPLE SEPARATION ))))))) Types SENSORS WITH SAMPLE SEPARATION Thermometric devices based on the measurement of the heat effects of a specific chemical reaction or adsorption which involve the analyte. In this group the heat effects may be measured in various ways, for example in the so called catalytic sensors the heat of a combustion reaction or an enzymatic reaction is measured by use of a thermistor. Magnetic devices based on the change of paramagnetic properties of a gas being analysed. These are represented by certain types of oxygen monitors.

))))))) Types Sensors Sensors have also been classified according to the application to detect or determine a given analyte. Examples are sensors for pH, for metal ions or for determing oxygen or other gases. Chemical sensors may be according to the mode of application, for example sensors intended for use in vivo, or sensors for process monitoring and so on.

))))))) Types A device that detects the smell more effectively then the human sense of smell. Consists of a mechanism for chemical detection. The electronic nose is an intelligent sensing device that uses an array of gas sensors which are overlapping selectively along with a pattern reorganization component.  Electronic Nose Commercial industries, agriculture, biomedical, cosmetics, environmental, food, water and various scientific research fields. usage

))))))) Types The smells are composed of molecules, which has a specific size and shape. Each of these molecules has a corresponding sized and shaped receptor in the human nose. When a specific receptor receives a molecule it sends a signal to the brain and brain identifies the smell associated with the particular molecule. The electronic noses work in a similar manner of human. The electronic nose uses sensors as the receptor. When a specific sensor receives the molecules, it transmits the signal to a program for processing, rather than to the brain. Electronic Nose

))))))) Types Electronic Nose ……………………………

))))))) Types The electronic nose was developed in order to mimic human olfaction whose functions are non separate mechanism , i.e. the smell or flavor is perceived as a global finger print. Essentially the instrument consists of sensor array, pattern reorganization modules, and headspace sampling, to generate signal pattern that are used for characterizing smells. The electronic nose consists of three major parts which are detecting system, computing system, sample delivery system. Electronic Nose

))))))) Types Electronic Nose --------------------- -----------

The sample delivery system: ))))))) Types The sample delivery system:  Enables the generation of headspace of sample or volatile compounds which is a fraction analyzed. The system then sends this head space into the detection system of the electronic nose. The detection system: Consists of a group of sensors is the reactive part of the instrument. When in contact with volatile compounds at that time the sensors reacts causing changes in electrical characteristics. Electronic Nose

Types Electronic Nose The Computing system: ))))))) Types The Computing system:  In most electronic noses each sensor is sensitive to all molecules in their specific way. However in bioelectric noses the receptor proteins which respond to specific smell molecules are used. Most of electronic noses use sensor arrays that react to volatile compounds. Whenever the sensors sense any smell , a specific response is recorded that signal is transmitted into the digital value. Electronic Nose Metal oxide semiconductor (MOSFET) Conducting polymers Quartz crystal microbalance Piezoelectric sensors Metal Oxide sensors usage

))))))) Types Electronic Nose

))))))) Types Electronic Nose

))))))) Conclusion coatings and films with improved properties for enhanced sensor performance (e.g., chemical selectivity, chromatographic efficiency, stability under electric field gradients, electrocatalysis efficiency); materials that enhance detector sensitivity and increase performance range (fiber optics); fiberoptic materials with improved performance in the near-infrared and infrared spectral regions; technologies for cost-effective miniaturization of sensor systems; on-chip formats for practical applications of miniaturized sensor systems; and chemical sensor systems with increased ruggedness, reliability, and control.

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