ELECTROCHEMICAL SENSORS FOR HEALTH MONITORING
By-M.MUHURTHCIVIL ‘A’ SECTIONROLL NO-41
ASPECTS IN CIVIL
ENGINEERING
ELECTROCHEMICAL SENSORS IN
MONITORING CHLORIDE INGRESS IN CONCRETE
STRUCTURES
OVERVIEW OF CORROSION IN CONCRETE
THRESHOLD LIMITS OF CHLORIDE IN CONCRETE ALLOWED LIMIT IN CONCRETE
0.05 %wt. (by mass of concrete)0.4 %wt. (by mass of cement)− 0.85 g of salt (max)
allowed in 1 L (or 1.7 kg) of concreteor 1.89 lb/cu. yd. ALLOWED LIMIT IN STEEL
Steel corrodes when the chloride content is 0.6 times the concentration of [OH¯ ]
If the pH = 12.9, [OH¯ ] = 1x10-1.1 M; and [Cl¯ ] = 48 mM
SENSING CHLORIDE
CASE STUDY
CLORIDE SENSORS SUMMARY
THE SENSOR PREDICTED-problems at site #1-found site#2 concrete was good
ASPECTS IN
ELECTICALS
1. ELECTRICALS IN CHLORIDE INGRESS IN MONITORING OF CONCRETE STRUCTURES
2. SWEAT SENSING BELT
CHLORIDE THRESHOLD SENSOR
CIRCUIT DIAGRAM
SWEAT SENSING BELT
ARCHITECTURE OF SWEAT SENSORS
USES
1.Detection of cystic fibrosis
Clinical interest in sweat electrolyte analysis includes the diagnosis of Cystic Fibrosis (CF),indicated by abnormally high sodium levels in sweat
2.Dehydration monitoring in athletes
More the dehydration more will be the concentration of sodium therefore more will be the output from the sensor hence indicating the level of dehydration
ASPECTS IN PHYSICS
Electrochemical sensors for clinical analysis
PRINCIPLES
POTENTIOMETRIC ELECTROCHEMICAL SENSORS
In potentiometric sensors, the potential difference between the reference electrode and the indicator electrode is measured without polarizing the electrochemical cell
Amperometric electrochemical sensors Amperometry is a method of
electrochemical analysis in which the signal of interest is a current that is linearly dependent upon the concentration of the analyte
APPLICATION:CHEMICAL FIELD EFFECT TRANSISTOR FOR THE DETECTION OF UREA ChemFET, or chemical field-effect transistor,
[1] is a type of a field-effect transistor acting as a electrochemical sensor. It is a structural analog of a MOSFET transistor, where the charge on the gate electrode is applied by a chemical process. It may be used to detect atoms, molecules, and ions in liquids and gases.
Its detection principle is based on the production of acidic or basic chemical species due to the urease enzymatic reaction.
There will be a ph sensor associated with the chemFET according to the concentrations of ph the signal is generated in the transistor based on the standard concentrations the urea can be detected in the blood sample
ASPECTS IN MATHEMATICS
1.ENVIRONMENTAL HEALTH MONITORING USING ELECTROCHEMICAL GAS SENSORS
GAS SENSORS Gas sensor is a subclass of chemical sensors.
Gas sensor measures the concentration of gas in its vicinity. Gas sensor interacts with a gas to measure its concentration. Each gas has a unique breakdown voltage i.e. the electric field at which it is ionized. Sensor identifies gases by measuring these voltages. The concentration of the gas can be determined by measuring the current discharge in the device
APPLICATIONS OF GAS SENSOR:
Process control industries Environmental monitoring Boiler control Fire detection Alcohol breath tests Detection of harmful gases in mines Home safety Grading of agro-products like coffee and
spices
FORMULA USED IN GAS SENSOR I = F × (A/σ) × D × C × n where:
I: Sensor outputF: Faraday constant= = 9.648 70 x 104, coulombs/faraday(C mol-1).A: Surface area of diffusion filmσ: Thickness of diffusion filmD: Gas diffusion coefficientC: Gas concentrationn: Number of reaction electrons
The linear relationship of gas concentration to sensor output makes this technology ideal for gas sensing applications.
DISADVANTAGES Bulky Consume lots of power Require “risky” high voltage to operate.
DEVELOPMENT There is a recent progress in developing MEMS (Micro-
Electro-Mechanical Systems) based H2 gas sensors. These sensors couple novel thin films as the active layer with a MEMS structure known as a Micro-Hotplate. This coupling results in a H2 gas sensor that has several unique advantages in terms of speed, sensitivity, stability and amenability to large scale manufacture. Preliminary results are extremely encouraging and suggest that this technology has substantial potential for meeting the sensing requirements of a hydrogen based energy economy.
NERNST EQUATION
the Nernst equation is an equation that relates the reduction potential of a half cell (or the total voltage, i.e. the electromotive force, of the fuel cell) at any point in time to the standard electrode potential, temperature, activity, and reaction qoutient of the underlying reactions and species used.
Ecell = E0cell - (RT/nF)lnQEcell = cell potential under
nonstandard conditions (V)E0
cell = cell potential under standard conditionsR = gas constant, which is 8.31 (volt-coulomb)/(mol-K)T = temperature (K)n = number of moles of electrons exchanged in the electrochemical reaction
CONCLUSION electrochemical sensors are widely
used in all the branches of science Chloride threshold sensors helps in
monitoring of the structures and hence predicting the life of the structures
They are also helpful in monitoring the human body and hence it is important in medical sciences
They are also helpful in monitoring our environment
Thus electochemical sensors are the chief aspect in various fields mainly in health monitoring related to various apects
REFERENCES IEEE EXPLORER .E. J. Gannon and P.D. Cady, Condition Evaluation of Concrete
Bridges Relative to Reinforcement Corrosion, Vol. 1: State ofthe Art of Existing Methods, Publication No. SHRP-S/FR-92-103, Strategic Highway Research Program, Washington, D.C.(1992).
@J. Kumar and P. and Chambon, "the estrogen receptor binds tightly toits responsive element as a ligand induced homodimer," cel1,vol. 55,pp. 1456, 1988
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