Download A sensor converts one form of energy to converts the measurand (a

1/2/2017
Prof. Steven S. Saliterman
Introductory Medical Device Prototyping
Department of Biomedical Engineering, University of Minnesota
www.tc.umn.edu/~drsteve
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A sensor converts one form of energy to
another, and in so doing detects and conveys
information about some physical, chemical or
biological phenomena.
More specifically, a sensor is a transducer that
converts the measurand (a quantity or a
parameter) into a signal that carries
information.
For our purposes, we are generally trying to
convert the measurand into an electrical signal
that can be input into a microcontroller.
Prof. Steven S. Saliterman
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Something in our environment:
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Biomedical:
◦ Ambient temperature, barometric pressure, humidity,
gas, light, dust, air quality, water quality, soil moisture,
and radiation.
◦ Blood pressure, pulse, body temperature, height, weight,
respiratory rate, laboratory (blood, urine, cerebral spinal
fluid); respiratory and blood gasses, flow (blood, urine
and air), intraocular, intracranial and tympanic
membrane pressures; electrocardiogram, electrical
activity of muscles and nerves, and internal organ
imaging (x-ray, ultrasound, camera, NMR).
Prof. Steven S. Saliterman
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Other physical measurements:
◦ Stress, stain, strength, pressure, distances,
magnetic fields, sound, light, water levels, motion
(acceleration), orientation (gyro), proximity and
location (GPS).
Images
User interactions:
◦ Tactile, button presses, flexion, knob turning; hand
and other body part motion, and eye movement
tracking.
Prof. Steven S. Saliterman
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Sensors may be classified based on the following:
◦ Measurand - temperature, pressure, flow etc.
◦ Transduction (physical and chemical effects) - SAW, ion
selective FETs, optodes (chemical transducer) etc.
◦ Materials - resistive, piezoelectric, magnetic, permeable
membranes, etc.
◦ Technology – MEMS, bioMEMS, plasmon resonance,
CMOS imaging, charge coupled devices etc.
◦ Energy requirement - active or passive.
◦ Applications - industrial, automative, aviation, consumer
electronics, biomedical etc.
Prof. Steven S. Saliterman
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Continuous operation without effecting the
measurand.
Appropriate sensitivity and selectivity.
Fast and predictable response.
Reversible behavior.
High signal to noise ratio.
Compact
Immunity to environment.
Easy to calibrate.
Prof. Steven S. Saliterman
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Prof. Steven S. Saliterman
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If the bridge resistors have the same
value, equal to the strain gauge's
resistance at rest, then the voltage is
zero.
The voltage can be amplified to get a
higher sensitivity for the complete
circuit.
This can be done with a high gain
instrumentation amplifier
The instrumentation amplifier inputs
replace the volt meter in the top
circuit.
Karki, J. Texas Instruments: Signal Conditioning
Wheatstone Resistive Bridge Sensors. Application Report,
SLOA034, September 1999.
Direct transduction from mechanical to electrical
domains and vice versa. May be used as sensors or
actuators.
The reversible and linear piezoelectric effect
manifests as the production of a charge (voltage)
upon application of stress (direct effect) and/or as the
production of strain (stress) upon application of an
electric field (converse effect).
Three modes of operation depending on how the
piezoelectric material is cut: transverse, longitudinal
and shear.
Amplifiers are needed to detect the small voltage.
Prof. Steven S. Saliterman
Tadigadapa, S., and K. Mateti. 2009. Piezoelectric MEMS
sensors: state-of-the-art and perspectives. Measurement
Science & Technology 20, no. 9:092001.
Converse Piezoelectric Effect - Application of an electrical field
creates mechanical deformation in the crystal.
Polling - Random
domains are aligned
in a strong electric
field at an elevated
temperature.
Direct Piezoelectric Effect - When a mechanical stress (compressive or
tensile) is applied a voltage is generated across the material.
Prof. Steven S. Saliterman
Adopted from bme240.eng.uci.edu
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The piezoelectric effect is a linear phenomenon where
deformation is proportional to an electric field:
S = dE and D = dT
W h ere
S is th e m ech an ical strain ,
d is th e piezo electric co efficient,
E is th e electric field ,
D is the d isp lacm ent (o r ch arg e d en sity ) lin early, an d
T is th e stress.
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These equations are known as the converse
piezoelectric effect and the direct piezoelectric effect
respectively.
Prof. Steven S. Saliterman
Prof. Steven S. Saliterman
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Crystals
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Ceramics
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Tadigadapa, S., and K. Mateti. 2009. Piezoelectric MEMS
sensors: state-of-the-art and perspectives. Measurement
Science & Technology 20, no. 9:092001.
Quart SiO2
Berlinite AlPO4
Gallium
Orthophosphate GaPO4
Tourmaline (complex chemical structure)
◦ Barium titanate BaTiO3
◦ Lead zirconate titanate PZT, Pb [ZrxTi1-x] O3 ; x = 0,52
Other Materials
◦ Zinc oxide ZnO
◦ Aluminum nitride AlN
◦ Polyvinylidene fluoride PVDF
Prof. Steven S. Saliterman
Adopted from Piezomaterials.com
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V O ut  
 RF 
QT


C T  C P  R1 
V O ut  
Prof. Steven S. Saliterman
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Tadigadapa, S., and K. Mateti. 2009. Piezoelectric MEMS
sensors: state-of-the-art and perspectives. Measurement
Science & Technology 20, no. 9:092001.
Piezoelectric sensors maybe configured as direct
mechanical transducers or as resonators.
The observed resonance frequency and amplitude
are determined by the physical dimensions,
material and mechanical and interfacial inputs to
the device.
Prof. Steven S. Saliterman
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QT
CF
Tadigadapa, S., and K. Mateti. 2009. Piezoelectric MEMS
sensors: state-of-the-art and perspectives. Measurement
Science & Technology 20, no. 9:092001.
Generation of surface acoustic waves (SAW) in
quartz by interdigitated transducers:
Prof. Steven S. Saliterman
Gardner, JW, VK Varadan and OO Awadelkarim, Microsensors, MEMS
and Smart Devices. John Wiley & Sons, Ltd. W. Sussex (2001).
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Typically with a sensing film such polyimide deposited on the
surface in the area between the interdigitated transducers:
Prof. Steven S. Saliterman
Prof. Steven S. Saliterman
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Gardner, JW, VK Varadan and OO Awadelkarim, Microsensors, MEMS
and Smart Devices. John Wiley & Sons, Ltd. W. Sussex (2001).
Tadigadapa, S., and K. Mateti. 2009. Piezoelectric MEMS
sensors: state-of-the-art and perspectives. Measurement
Science & Technology 20, no. 9:092001.
Biomedical Micro Electro-Mechanical Systems.
(The science of very small biomedical devices.)
Subset of MEMS/MST (Microsystem Technology).
At least one dimension from ~100 nm to 200 µm
New materials, understanding of the
microenvironment, and biocompatibility.
Harnessing any phenomenon that accomplishes
work at the microscale.
Work may be at the microscale alone, or through
some multiplication process at the macroscale.
Prof. Steven S. Saliterman
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Reactive ion etching –
a subtractive process.
Low pressure chemical vapor deposition
(LPCVD)- an additive process.
Prof. Steven S. Saliterman
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Laboratory Diagnostic Tools:
◦ Microsensors & Microactuators,
◦ Lab-on-a-Chip Devices (LOC),
◦ Micro Total Analysis Systems (µTAS),
◦ DNA and Protein Microarrays.
Individualized Treatments
Tissue Scaffolding Devices
Medication Delivery Devices
Minimally Invasive Procedures
Platform for Nanomedicine Technologies
Homeland Security
Prof. Steven S. Saliterman
Image Courtesy of Sandia National Laboratories
Sub-µm IDEs
Surface Acoustic Wave
Polymer FETs
(proteins, DNA)
(proteins)
(pH, glucose)
© KdK20 02
Magnetic-bead
Biosensor
Transmission Plasmon
Biosensor
(proteins, DNA)
(proteins, DNA)
Prof. Steven S. Saliterman
GaAs MESFETs
(neurons, proteins)
Image Courtesy of Campitelli A, IMEC
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Piezoresistive pressure
sensor with reference
pressure cavity inside chip.
Prof. Steven S. Saliterman
Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical
Systems. Japanese Journal of Applied Physics 51, no. 8:080001.
Integrated capacitive
pressure sensor
fabricated by wafer level
packaging.
Prof. Steven S. Saliterman
Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical
Systems. Japanese Journal of Applied Physics 51, no. 8:080001.
Principle and photograph of SAW passive wireless pressure sensor and
example of measurement (change in time converted into phase).
Prof. Steven S. Saliterman
Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical
Systems. Japanese Journal of Applied Physics 51, no. 8:080001.
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Common two-wire tactile sensor network that sequentially selects sensors.
Prof. Steven S. Saliterman
Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical
Systems. Japanese Journal of Applied Physics 51, no. 8:080001.
Schematic of event-driven
(interrupt) tactile sensor
network, example of
operation, and photographs
of prototype IC.
Prof. Steven S. Saliterman
Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical
Systems. Japanese Journal of Applied Physics 51, no. 8:080001.
Poly-Si surface micromachined
integrated accelerometer (cross
sectional structure and
photographs of two-axis
accelerometer).
Prof. Steven S. Saliterman
Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical
Systems. Japanese Journal of Applied Physics 51, no. 8:080001.
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Schematic of accelerometer
with thick epitaxial poly-Si
layer and photograph of
resonant gyroscope.
Prof. Steven S. Saliterman
Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical
Systems. Japanese Journal of Applied Physics 51, no. 8:080001.
Automotive sensor
for yaw rate and
acceleration.
Prof. Steven S. Saliterman
Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical
Systems. Japanese Journal of Applied Physics 51, no. 8:080001.
Two-axis resonant
gyroscope used for image
stabilization (photograph
and schematic).
Prof. Steven S. Saliterman
Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical
Systems. Japanese Journal of Applied Physics 51, no. 8:080001.
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Apollo 11 Gyroscope 1969
Gyroscope image courtesy of
https://www.flickr.com/photos/blafetra/14524883649
Prof. Steven S. Saliterman
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Absolute Orientation (Euler Vector, 100Hz) Three axis
orientation data based on a 360° sphere.
Absolute Orientation (Quaterion, 100Hz) Four point
quaternion output for more accurate data manipulation.
Angular Velocity Vector (100Hz)
Three axis of 'rotation speed' in rad/s.
Acceleration Vector (100Hz)
Three axis of acceleration (gravity + linear motion) in
m/s^2.
Magnetic Field Strength Vector (20Hz) Three axis of
magnetic field sensing in micro Tesla (uT).
Linear Acceleration Vector (100Hz) Three axis of linear
acceleration data (acceleration minus gravity) in m/s^2.
Gravity Vector (100Hz) Three axis of gravitational
acceleration (minus any movement) in m/s^2.
Temperature (1Hz) Ambient temperature in degrees
celsius.
Prof. Steven S. Saliterman
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Apollo Command Module 1973
S. Saliterman
Courtesy of Adafruit
Platinum resistor:
◦ Linear, stable, reproducible.
◦ Material property dependency on temperature,
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Thermocouples (e.g. Type K)
Thermistor: a semiconductor device made of
materials whose resistance varies as a
function of temperature.
Thermodiode and Thermotransistor.
Prof. Steven S. Saliterman
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Potentiometric devices fabricated by the joining of
two different metals forming a sensing junction:
◦ Based on the thermoelectric Seebeck effect in which a
temperature difference in a conductor or semiconductor
creates an electric voltage:
D V = asD T
W h ere
D V is th e electrical v o ltag e,
a s is the S eeb eck co efficien t ex p ressed in v o lts/K  , and
D T is th e tem p erature d ifferen ce ( T S - Tref ).
Prof. Steven S. Saliterman
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Gardner, JW, VK Varadan and OO Awadelkarim, Microsensors, MEMS
and Smart Devices. John Wiley & Sons, Ltd. W. Sussex (2001).
When a p-n diode is operated in a constant current
(IO) circuit, the forward voltage (Vout) is directly
proportional to the absolute temperature (PTAT).
V o ut =
ö÷
k B T æç I
ln çç + 1÷÷÷
q
÷ø
èç I S
W here
k b is the B olzm an constant,
T is tem peratu re,
q is the charg e on an electron,
I is the op eratin g current and
I S is the saturation current.
Prof. Steven S. Saliterman
Gardner, JW, VK Varadan and OO Awadelkarim, Microsensors, MEMS
and Smart Devices. John Wiley & Sons, Ltd. W. Sussex (2001).
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Hot wire or hot element anemometers.
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Calorimetric sensors.
◦ Based on convective heat exchange taking place
when the fluid flow passes over the sensing
element (hot body).
◦ Operate in constant temperature mode or in
constant current mode.
◦ Based on the monitoring of the asymmetry of
temperature profile around the hot body which is
modulated by the fluid flow.
Prof. Steven S. Saliterman
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The heat transferred per unit time from a
resistive wire heater to a moving liquid is
monitored with a thermocouple:
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Prof. Steven S. Saliterman
Gardner, JW, VK Varadan and OO Awadelkarim, Microsensors, MEMS
and Smart Devices. John Wiley & Sons, Ltd. W. Sussex (2001).
In a steady state, the mass flow rate can be determined:
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Qm =
dm Ph
= (T -T )
dt cm 2 1
Where
Q m is the mass flow rate,
Ph is the heat transferred per unit time,
c m is the specific heat capacity of the fluid and
T1 ,T2 are temperature.
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The volumetric flow rate is calculated as follows:
QV =
dV Qm
=
dt ρm
Where
Q V is the volumetric flow rate,
Q m is the mass flow rate and
ρ m is the density.
Prof. Steven S. Saliterman
Prof. Steven S. Saliterman
Silvestri, S. and E. Schena Micromachined Flow Sensors in
Biomedical Applications. Micromachines 2012, 3, 225-243
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Cantilever type flow sensors
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Differential pressure-based flow sensors
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Measuring the drag-force on a cantilever beam.
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When a fluid flow passes through a duct, or over a surface, it produces a pressure drop
depending on the mean velocity of the fluid.
Electromagnetic
Laser Doppler flowmeter
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The phenomenon is due to the interaction between an electromagnetic or acoustic wave
and a moving object: the wave is reflected back showing a frequency different from the
incident one.
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Lift-force and drag flow sensors
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Microrotor
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Based on the force acting on a body located in a fluid flow.
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Rotating turbine
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Temperature effects resonance frequency of a vibrating membrane.
Resonating flow sensors
Prof. Steven S. Saliterman
Silvestri, S. and E. Schena Micromachined Flow Sensors in
Biomedical Applications. Micromachines 2012, 3, 225-243
Able to Sense Direction
Prof. Steven S. Saliterman
Silvestri, S. and E. Schena Micromachined Flow Sensors in
Biomedical Applications. Micromachines 2012, 3, 225-243
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Potentiometric Sensors
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Voltametric Sensors
◦ Ion selective electrodes (ISE) into the nanodimension range
◦ New ion recognition chemistries
◦ New ion selective membranes
◦ Importance of the reference electrode
◦ Carbon paste electrodes (CPE) for organic
molecule detection
◦ Micro and Ultramicro electrodes
◦ Environmental monitoring
◦ Carbon nanotubules
◦ Stripping voltammetry
Prof. Steven S. Saliterman
Privett, Benjamin J., Jae H. Shin, and Mark H. Schoenfisch. 2010.
Electrochemical Sensors. Analytical Chemistry 82, no. 12:4723-4741.
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Electrochemical Biosensors
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Immunosensors
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Ion Selective Field Effect Transistors
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Selective and sensitive biological binding
Aptamer-based biosensors
Glucose, creatinine, pathologic bacteria, DNA
Enzyme biosensors
◦ Bacteria, virus and cancer biomarkers
◦ Based on the electrochemical phenomena occurring
within the chemically sensitive membrane placed on
top of the transistor gate and on electrical
transduction of the signal by this semiconductor
device.
Privett, Benjamin J., Jae H. Shin, and Mark H. Schoenfisch. 2010.
Electrochemical Sensors. Analytical Chemistry 82, no. 12:4723-4741.
Prof. Steven S. Saliterman
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Photocurable polymers have been used for
encapsulation of ion selective field effect transistors
(ISFET) and for membrane formation in chemical
sensitive field effect transistors (ChemFET).
D
G
Charge Carriers In
D
Charge Carriers Out
G
S
PChannel
S
NChannel
Shown: Insulated Gate Field-Effect Transistor
(IGFET). MOSFET (metal oxide is common).
Abramova, Natalia, and Andrei Bratov. 2009. Photocurable
Polymers for Ion Selective Field Effect Transistors. 20 Years of
Applications. Sensors 9, no. 9:7097-7110.
Prof. Steven S. Saliterman
Silicon (semiconductor) substrate
-- -
- - -
+ + + + + ++ +
A
G
B
S
+ + + ++++ +
+
+ +
- - -- -- - -
D
A small signal on the plate above (gate) brings electrons to the
surface, allowing current to flow and amplifying the original signal.
Prof. Steven S. Saliterman
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Polyimide covered by a standard photoresist and photocurable epoxy
acrylate.
The polymer layer after being applied to a wire bonded sensor glued
to some substrate can be patterned using traditional
photolithography techniques.
Left: ISFET with photocurable encapsulate (1), with openings over the
gate (2), contact pads (3) and scribing lines (4).
Center and Right: Mounting, wire bonding and encapsulation.
3mm opening
Prof. Steven S. Saliterman
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The best known method of ISFET membrane
formation comes from traditional ion selective
electrodes and is based on using a polymer
matrix which is deposited over an ISFET gate and
contains the required ion active components, like
ionophore, plasticizer and lipophilic additives.
Achievements in development of traditional ISE
with liquid inner contact resulted in hundreds of
different membrane compositions that can be
used as well in case of ISFETs.
Prof. Steven S. Saliterman
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Abramova, Natalia, and Andrei Bratov. 2009. Photocurable
Polymers for Ion Selective Field Effect Transistors. 20 Years of
Applications. Sensors 9, no. 9:7097-7110.
Abramova, Natalia, and Andrei Bratov. 2009. Photocurable
Polymers for Ion Selective Field Effect Transistors. 20 Years of
Applications. Sensors 9, no. 9:7097-7110.
Optical chemical sensors are usually configured as
transducers, with transductions steps of electricaloptical-chemical-optical-electrical conversion:
Prof. Steven S. Saliterman
Boisde, G. and A. Harmer, Chemical and Biochemical Sensing
with Optical Fibers and Waveguides, Artech House, Boston (1996)
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Esashi, Masayoshi. 2012. Revolution of Sensors in
Micro-Electromechanical Systems. Japanese Journal of
Applied Physics 51, no. 8:080001.
Prof. Steven S. Saliterman
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An optical fiber consists of a solid cylindrical core of
transparent material surrounded by a cladding of
similar material but of lower refractive index than the
core:
Prof. Steven S. Saliterman
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The refractive index is the ratio of the speed of light
in a vacuum to the speed of light in the medium:
n=

c vacuum
³1
c m aterial
Snell’s law defines the relationship between incident
and refracted light, measured as an angle from a
perpendicular to the surface:
n i sin I = n r sin R
Prof. Steven S. Saliterman
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Glucose and anticoagulation monitoring:
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Prof. Steven S. Saliterman
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Images courtesy of LifeScan, Inc. and HemoSense, Inc.
Temperature:
Image courtesy of Braun
Prof. Steven S. Saliterman
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Harsanyi, G., Sensors in Biomedical Applications, Technology and
Applications. Technomic Pub. Co., Lancaster, PA (2000)
Pressure:
Prof. Steven S. Saliterman
Fraden, J. “Noncontact temperature measurement in medicine.”
Bioinstrumentation and Biosensors, D.L. Wise, Ed, Marcel Dekker (1991).
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Intraocular pressure:
Prof. Steven S. Saliterman
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Bergveld, A.P., “The merit of using silicon for the development of
hearing aid microphones and intraocular pressure sensors.” Senors and
Actuators 41:42, pp. 223-229 (1994)
Pulse oximetry:
Prof. Steven S. Saliterman
Prof. Steven S. Saliterman
Parker, D. “Sensors for monitoring blood gasses in intensive
care.” J Phys. E. Sci. Instrum. 20, pp. 1103-1112 (1987).
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Respiratory – spirometry and CO2:
Prof. Steven S. Saliterman
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Implanted pacemaker and rhythm monitor:
Prof. Steven S. Saliterman
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What are sensors and what do we sense?
Sensor Classification and ideal sensor.
Piezoelectric effect and SAW.
MEMS & bioMEMS
Thermo and thermo flow sensors
Electrochemical sensors
Ion Selective Field Effect Transistors
Optical sensors
Clinical applications
Prof. Steven S. Saliterman
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