Lecture 11 - Weber State UniversityApplications of Wearable Biosensors Chemical and Vital Sign Sensors and Firefighter Saftey Reduce deaths and disability due to Cardiac stress by

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

ECE 5900/6900: Fundamentals of Sensor Design

Lecture 11Biomedical Sensor Systems & Biosensors

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Biomedical Sensors and BioSensors

Q: What are biomedical sensor systems?

A: Sensor systems 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

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Biomedical Sensor Systems

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Blood Pressure Monitor

Pulse Oximeter

Respiratory Monitor

ECG Monitor

Omron

BP792IT

Covidien

Nellcor

System

Strong

Digital

Handheld

Pulse

Oximeter

703A

Heal Force Prince 180B

Portable ECE Monitor

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Ultrasound

Machine

Defibrillators

Portable X-Ray Machine

Xavier

portable

x-ray

GE Voluson

E10

Phillips Heartstart XLdefibtech

Lifeline

AED

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Applications of Biomedical Sensors

Ref: Q-CPR® Measurement and Feedback with CPR meter, Application Note by Phillips

1) Provide audio/visual feedback to

the CPR giver

2) Chest compression sensor

measures compressions and

ventilations connected to the

defibrillator

CPR Meter and Emergency Medical Attention

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Ref: Lionsgate technologies (LGT Medical)

1) Pulse Oximeters measure Oxygen levels in blood and heart rate

2) Measure oxygenation level for intensive care, operating, recovery, emergency and

hospital ward settings, pilots in unpressurized aircraft

Pulse Oximeter and Oxygenation Level

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Ref: TE Connectivity and GE Healthcare

1) Ultrasound systems perform nondestructive testing of body structures and

provide medical imaging

2) Visualize subcutaneous body structures including tendons, muscles, joints,

vessels and internal organs for possible pathology or lesions

Ultrasound and Diagnostic imaging

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Ref: TE Connectivity and GE Healthcare

1) AEDs can measure heart signals and send out electric shock as

needed

2) AEDs can save lives!

Automatic External Defibrillator (AED) and Restoration of Heart Rhythm

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Types of Biomedical Sensor Systems

ECG Signal Monitor

Glucose Sensor

Ultrasound Machine

Defibrillator

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Electric System of Heart

Ref: https://www.uahealth.com/library/sections/article/electrocardiogram-ekg-stress-test-holter-monitor

1) ECG Signal is a sum of many different heart signals (cell potential)

2) Heart can be viewed as time-varying voltage source with amp= sum of

cardiac cell potentials and freq= cardiac cycle

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ECG Signal: Abnormalities

Normal

Tachycardia: fast heart rate

Extrasystole - Premature Beat

Ventricular fibrillation: uncoordinated

ventricular contractions

Complete heart block: signal from atria not

reaching ventricles which beat on their own

Myocardial Infarction: disruption due to death

of tissue

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ECG Signal Amplifier Circuit#1Goal: Amplify the raw ECG signal level while suppressing noise

1) Right Leg (RL) drive circuit reduces interference and DC offset out of the

differential amplifier.

2) RL drive circuit inverts and amplifies the average common mode signal back

into the patient’s right leg and creates a cleaner ECG output signal.

3) Larger feedback gain improves the common mode rejection ratio (CMRR)

Typical ECG signal amp=between 10uV and 5 mV, bandwidth=between 0.05 and 100.00 Hz

+-

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ECG Signal Amplifier Circuit#3Goal: Amplify the raw ECG signal level while suppressing noise

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ECG Signal Noise and Artefacts

Power line noise snubber

(60 Hz Bandpass Filter)

Most artefacts

can be filtered digitally

[1] ECG Signal Amplifier Circuit: http://www.egr.msu.edu/classes/ece480/capstone/spring13/group03/documents/ElectrocardiographyCircuitDesign.pdf

http://www.cisl.columbia.edu/kinget_group/student_projects/ECG%20Report/E6001%20ECG%20final%20report.htm

[2] Labview VI: http://www.ni.com/tutorial/6349/en/

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ECG Signal Monitor

Glucose Sensor

Ultrasound Machine

Defibrillator

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Glucose sensor

Thermistor

Control, Working and

Reference Electrodes

Amperometry Circuit

Glucose -> Glucose Oxidase -> Ions -> Change in Current (3 μA)

fc = 100 HzTest Strip

Test Strip

MeterTiny

blood drop

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ECG Signal Monitor

Glucose Sensor

Ultrasound Machine

Defibrillator

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Ultrasound Basics

1) Transducers generate ultrasound waves (2 -18 MHz), which are sent to the

tissue and internal organs by creating better acoustic coupling with ultrasound gel

2) Ultrasound waves hit a boundary between tissues, part of the sound waves get

reflected back to the transducer while some sound waves propagate further until

they hit another tissue boundary and get reflected

3) By receiving and processing the echoes, the 2D and 3D image of the internal

organs and structures can be formed

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Ultrasound Imaging System: Microchip

Ref: Microchip http://www.microchip.com/pagehandler/en-us/technology/ultrasound/home.html

Generic Ultrasound System

Phased array transducers (32 to 256 transmitter/receiver pairs)

High Voltage Analog Switch, High Voltage Transmitter,

High voltage FET and FET Array, FET Driver, Arbitrary Waveform

Generator, and T/R Switch.

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Ultrasound Imaging System: Maxim Integrated

Ref: Maxim Integratedhttps://www.maximintegrated.com/en/app-notes/index.mvp/id/4696

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Ultrasound TransmitterHigh Voltage Analog Switch:

1) Acts as multiplexer to dynamically connect a specific transducer element

to a specific transmitter/receiver (Tx/Rx) pair.

2) Must handle voltage swings as large as 200VPP and with peak currents

up to 2A.

High Voltage Transmitter:

1) Transmitter beamformer typically generates the necessary digital

transmit signals with the proper timing and phase to produce a focused

transmit signal

2) Arbitrary waveform generator is used to opimize image quality: the

transmitter generates digital 8-bit to 10-bit words at rates of

approximately 40MHz to produce the required transmit waveform.

Digital-to-analog converters (DACs)

1) DACs are used to translate the digital waveform to an analog signal,

which is then amplified by a linear high-voltage amplifier to drive the

transducer elements


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Ultrasound Receiver


Tx/Rx switch

1) Protects the LNA from the high-voltage transmit pulse and isolates the

LNA's input from the transmitter during the receive interval.

2) Diodes comprise the switch which automatically turn on and off when

presented with a high-voltage transmit pulse

Low-noise amplifier (LNA) and Variable-gain amplifier (VGA)

1) LNA must have excellent noise performance, low-input impedance and

sufficient gain

2) VGA provides the receiver with sufficient dynamic range (100 dB) over

the full receive cycle

3) Must have 30dB to 40dB of gain to amplify the received signal into a

typical 12-bit ADC

Anti-alias filter (AAF) and Analog-to-digital converter (ADC)

1) AAF reduces high-frequency noise (Butterworth or higher-order Bessel

filters)

2) 12-bit ADC at 40Msps to 60Msps

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ECG Signal Monitor

Glucose Sensor

Ultrasound Machine

Defibrillator

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Defibrillation Basics

1) Normal heart-beat can be restored by delivery of a controlled

electric shock: this process is called Defibrillation

2) Defibrillators include sensors that can detect the cardiac

rhythm and are programmed to deliver a right amount of shock

when required

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Defibrillator

Defibrillation can be performed by anyone

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Defibrillator System

Ref: Texas Instrumentshttp://www.ti.com/solution/automated_external_defibrillator

ECG Monitor

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Defibrillator CircuitThree key components: a high voltage source, a capacitor and

switches.

High Voltage Source

1) A battery drives an oscillator circuit which switches on and off at

1 kHz: the current is fed into transformer which generates about

500 V output

2) The AC signal is rectified by diode and is fed into the capacitor

Ref: Boston Scientifichttp://editions.sciencetechnologyaction.com/lessons/7/105/BostonScientific.pdf

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Defibrillator CircuitThree key components: a high voltage source, a capacitor and

switches.

Storage Capacitor

and Switches

1) High Voltage Caps

2) Switches charge and discharge (to the patient) the capacitor

3) Normal energy output = 125 J with C= 1mF, V=500 V (E = ½ C V2

4) V = 500 V, I=25 A, 10 ms pulse

Ref: Boston Scientifichttp://editions.sciencetechnologyaction.com/lessons/7/105/BostonScientific.pdf

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Biosensors

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Introduction

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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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Applications of Wearable 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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BioSensors and WBAN

Wearable pH Sensor

Wireless Body Area Network (WBAN)

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Basics of pH Sensing

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

during physical exercise and emotional stress

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

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

useful information regarding the wound

2) Help doctors diagnose cardiovascular diseases, cystic fibrosis or

others by acquiring physiological information on infants

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Basics of pH SensingMonitor Concentration of Hydrogen Ions

Number of hydrogen ions in water = pH level

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

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

lower pH

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

ions: this will lower hydrogen ions and increase pH

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Basics of pH SensingPotentiometric pH Sensing

Potentiometric sensors measure change in concentration of

electrons after redox reactions occur at the electrode-electrolyte

interface of an electrochemical cell

Oxidant + Ne- => Reduced product; N=number of electrons

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pH Sensors: CHEMFETCHEMFET (Chemical FET)

1) Silicon Nitride gate is exposed to the sample solution (e.g. sweat)

2) As H+ ion concentration (pH) changes, the redox reaction changes

the surface charge density at the gate: change in gate voltage

3) This change affects the channel conductance

4) The change in gate voltage is measured as a change in the

drain currentCheck out:

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

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pH Sensors: ISFETISFET (Ion Selective FET)

Type 2: Change e-

Concentration in the

Channel Changes Drain

Current

Type 1: Change in

Gate Voltage Changes

Drain Current

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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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BioSensors and WBAN

Wearable pH Sensor

Wireless Body Area Network (WBAN)

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Smart Sensors and Heath Technology

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Smart Sensors and Heath Technology

Documents

Lecture 11 - Weber State UniversityApplications of Wearable Biosensors Chemical and Vital Sign Sensors and Firefighter Saftey Reduce deaths and disability due to Cardiac stress by