1. IIIIII
Welcome

2. Monir Alrashid Hadya Mahmoud 20144018 Sandra dashan
Hadya Mahmoud
Sandra dashan
Lael rouhafzay
Aya chebib
Leila karimizarandi
Moath helal
Nuhu Abdulhaqq Isa
Biomedical Engineer
Biosensor BME301

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Introduction
Definition
Types
Conclusion

4. Chemical sensors are very different & quite common
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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.

5. Used in industry for process control and for monitoring for safety.
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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.

6. In sciences and in medicine - sampling of substances such as:
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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)

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

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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.

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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.

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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.

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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

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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

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Types
Direct
output
Indirect

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

15. SENSORS WITH SAMPLE SEPARATION
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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

16. SENSORS WITH SAMPLE SEPARATION
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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

17. SENSORS WITH SAMPLE SEPARATION
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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.

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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.

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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

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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

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Types
Electronic Nose
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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

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Types
Electronic Nose

24. The sample delivery system:
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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

25. Types Electronic Nose The Computing system:
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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

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Types
Electronic Nose

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Types
Electronic Nose

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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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Question