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).

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