Biomedical Sensors: Part 2 Wearable BioSensorsfaculty.weber.edu/snaik/ECE5900_ECE6900/12Lec12... ·...

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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik

EE 4900: Fundamentals of Sensor Design

Lecture 12Biomedical Sensors: Part 2

Wearable BioSensors

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Biomedical Sensors, BioSensors, and Wearable biosensors

Q: What are Biomedical sensors?

A: Sensors that measure vital signs such as ECG signal

(blood pressure, pulse rate), body temperature,

respiration rate and enzyme levels for glucose levels etc

Q: What are Biosensors?

A: Biosensor=bioreceptor+transducer

Biosensor is made up of bioreceptor which is a

biomolecule that recognizes target analyte and

transducer that converts the target event/species into

measurable signal

Q: What are Wearable biosensors?

A: Above two types of sensors on flexible substrate that

can be worn on body

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Wearable BioSensors

pH Sensor

Glucose SensorHealthpatch Sensor

Glaucoma Pressure/Glucose Sensor

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Wearable Biomedical Sensors

ECG Patch Sensor (biomedical)

Epilepsy Monitor Sensor (biomedical)

IMEC ECG Patch

Dialogue Device byArtefact

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Applications of Wearable Biomedical and Biosensors

Fighter Pilot Vitals and Health Status

Human Performance Augmentation (HPA) by measuring heart rate,

skin temperature, and blood pressure in real-time using wearable

biosensors to enhance warfighter performance

AFRL: http://www.wpafb.af.mil/news/story.asp?id=123402193

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E-nose and detection of Cortisol and Adrenaline

Detection of certain enzymes produced by body can help diagnose

lung cancer, heart failure, and kidney disorders

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Chemical and Vital Sign Sensors and Firefighter Saftey

Reduce deaths and disability due to Cardiac stress by tracking heart

and respiration rates, activity levels and posture

CO and CO2

Sensors

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Applications of BioSensors

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BioSensors and WBAN

Wearable pH Sensor

Healthpatch Bio Sensor

Wireless Body Area Network (WBAN)

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Biosensor Basics

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Bio Signals and Bio Sensing

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Basics of pH Sensor

Q: What do pH sensors measure?A: Sodium, chloride, lactate concentration in sweat produced

during physical excercise and emotional stress

Q: What are the applications of wearble pH sensors?A:

1) Wound monitoring: pH shifts at the wound site can provide

useful information regarding the wound

2) Help doctors diognose cardiovascular diseases, cystic fibrosis or

others by acquiring pysiological information on infants.

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pH Sensor typesColorimetric Detector

- Wearable micro-fluidic on reservoirs

PMMA and and pressure-sensitive

adhesive (PSA).

- Reservoirs contain ionogels

coated with four different pH sensitive

dyes

Ion Detector with RFID

- commercial RFID chip is adapted to allow potentiometric sensing

of 50 mM Na+ (sodium ions)

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pH Sensor typesElectrode Based

- Ion Selective Electrode (ISE) IrOx (Iridium Oxide) based needle

array

- Sensitivity of ∼62 mV/pH in the pH 2 to 12 range

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Basics of pH SensingMonitor Concentration of Hydrogen Ions

The number of hydrogen ions that the water will receive determines

the pH

1) When an acid substance ends up in water, it will give up a

hydrogen ion to the water: this will increase hydrogen ions and pH

2) When a basic substance enters the water it will take up hydrogen

ions: this will lower hydrogen ions and pH

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Basics of Potentiometric Sensing

1) Potentiometric (measure voltage)

2) Amperometric (measure current)

3) Conductometric (measure conductivity)

Types of Electrochemical Sensors

Potentiometric sensors use the effect of the concentration on the

equilibrium of redox reactions occurring at the electrode-electrolyte

interface of an electrochemical cell

The redox reaction

takes on the electrode

surface

Oxidant + Ne- => Reduced product

N=number of electrons

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Basics of Potentiometric Sensing

Nernst Equation

• Co is the oxidant concentration

• CR is the Reduced Product

Concentration

• n is the number of electrons

transferred per redox reaction

• F is the Faraday constant

• T is the temperature

• R is the gas Constant

• E0 is the electrode potential at a

standard state.

The Nernst equation

gives the potential of

each half cell.

)(log 00

R

eC

C

nF

RTEE

In a potentiometric sensor, two half-

cell reactions take place at each

electrode:

1) Only one of the reactions should

involve sensing the species of interest.

2) The other should be a well

understood reversible and non-

interfering reaction

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pH Sensors: CHEMFET and ISFETCHEMFET (Chemical FET)

A lot of the art of CHEMFETs is in engineering

the porous layer over the gate.

Ion selective CHEMFET with a

silicon nitride gate for measuring

pH (H+ ion concentration)

1) Bare silicon nitride gate is exposed to

the sample solution

2) A change in the surface charge density

affects the channel conductance: change

in gate voltage is measured as a variation

in the drain current.Check out:

http://www.slideshare.net/RichardYang13/richard-yang-phd-defense-talk

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pH Sensors: CHEMFET and ISFETISFET (Ion Selective FET)

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pH Sensors: CHEMFET and ISFETISFET (Ion Selective FET)

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RFID pH Sensor

Ref: Adhesive RFID Sensor Patch for Monitoring of Sweat Electrolytes by D. Rose, et. al

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RFID pH Sensor System

Ref: Adhesive RFID Sensor Patch for Monitoring of Sweat Electrolytes by D. Rose, et. al

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pH Sensor IC

Ref: MLX90129 RFID Transponder http://www.melexis.com/Assets/Data-Sheet-MLX90129-5941.aspx

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BioSensors and WBAN

Wearable pH Sensor



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ECG Patch Sensors

V Patch by Intelesens

The patient wears the V Patch that connects to electrodes

Often an accelerometer is integrated to estimate of activity level

ECG is monitored continuously and events detected by the system are

transmitted to a base station (or bluetooth device)

From the base station, data is uploaded to a web-based interface

that can be accessed by the physician

The V patch can automatically detect a number of the most commonly

occurring arrhythmias, and responds patient alarm

ECG Patch by Imec

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ECG Patch Sensor RequirementsECG Signal Quality Requirements

Ref: A Long Term Wearable Electrocardiogram (ECG) Measurement System by M. Delano, M.S. Thesis, MIT

Driven Right Leg (DRL) scheme

Instrumentation Amplifier (INA) can

provide high CMRR but large potential

differences between the body and the sensor

system can result in common mode

voltages outside the IA's input range

Also 60 Hz interference is caused by

an impedance mismatch between the two sensing electrodes

Drive Right Leg (DRL) scheme is used to measure the common mode voltage

and negatively amplify the resulting signal and the body is driven to that

potential.

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Patch Sensor Circuit

Ref: A Long Term Wearable Electrocardiogram (ECG) Measurement System by M. Delano, M.S. Thesis, MIT

Running

Resting

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BioSensors and WBAN

Wearable pH Sensor



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Smart Sensors and Heath Technology

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