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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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
Wearable BioSensors
pH Sensor
Glucose SensorHealthpatch Sensor
Glaucoma Pressure/Glucose Sensor
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
Wearable Biomedical Sensors
ECG Patch Sensor (biomedical)
Epilepsy Monitor Sensor (biomedical)
IMEC ECG Patch
Dialogue Device byArtefact
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
Applications of Wearable Biomedical and Biosensors
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
Applications of Wearable Biomedical and Biosensors
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
Applications of BioSensors
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
BioSensors and WBAN
Wearable pH Sensor
Healthpatch Bio Sensor
Wireless Body Area Network (WBAN)
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
Biosensor Basics
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
Bio Signals and Bio Sensing
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
pH Sensors: CHEMFET and ISFETISFET (Ion Selective FET)
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
pH Sensors: CHEMFET and ISFETISFET (Ion Selective FET)
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
RFID pH Sensor
Ref: Adhesive RFID Sensor Patch for Monitoring of Sweat Electrolytes by D. Rose, et. al
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
RFID pH Sensor System
Ref: Adhesive RFID Sensor Patch for Monitoring of Sweat Electrolytes by D. Rose, et. al
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
pH Sensor IC
Ref: MLX90129 RFID Transponder http://www.melexis.com/Assets/Data-Sheet-MLX90129-5941.aspx
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
BioSensors and WBAN
Wearable pH Sensor
Healthpatch Bio Sensor
Wireless Body Area Network (WBAN)
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
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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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
BioSensors and WBAN
Wearable pH Sensor
Healthpatch Bio Sensor
Wireless Body Area Network (WBAN)
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
Smart Sensors and Heath Technology
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
Smart Sensors and Heath Technology
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ECE 5900/6900 Fundamentals of Sensor Design Dr. Suketu Naik
Smart Sensors and Heath Technology