Transcript Smart Sensors Based on Piezoelectric PVDF

Individuals Contributing to
This Project
Guillermo Carbajal-Franco, M. S.
Dr. M. P. Eastman
Dr. C. V. Ramana
Dr. Eric Hagedorn
Colleges of Science and Engineering
Consultants: Dr. R. C.
Hughes, Dr. T.L. Porter
Monday, March 28, 2016
PVDF- Basics
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Polyvinylidene difluoride (PVDF),is also known under
various trade names including _KYNAR (Trade Mark:
Elf Atochem North American) SOEF (Trade Mark:
Solvay S. A.)
PVDF is prepared by the polymerization of 1,1-vinylidene
F
H
difluoride
The structure of the monomer is:
F

The structure of the polymer is:
H
Representations of the molecular structure
of the vinylidene difluoride (VD) monomer
and of the a and b forms of the PVDF
polymer.
F
H
F
H
VD-wire
PVDF-b form
PVDF-a form
VD-space filling
Piezoelectric Materials
With piezoelectric materials have a separation of charge which generates a
net dipole in the case the dipoles are aligned (2),(3) below- stressing the
material generates a voltage. Materials with unaligned dipoles (1) are not
piezoelectric. Examples: Inorganic: barium titanate (BiTiO3) and lithium
niobate (LiNbO3); Biological materials: bone, tendons, sugar, dentin.
Polymers: PVDF.
http://en.wikipedia.org/wiki/Piezoelectricity
http://www.physikinstrumente.com/tutorial/
4_15.html
Important Properties of PVDF
Property
Units
Reported Value
Melting
C
174
Glass Transition
C
~ -30
Density
g/ cm3
1.8
Heat Capacity
Joule/(g K)
1.9
Tensile Strength
psi
78000
Serving Temperature
Long Term
C
140
Dielectric Constant (60
Hz)
-
9
Dielectric Strength
KV/mm
160
Volume Resistivity
Ohm/cm
1 x 1014
Refractive Index
1.42
PVDF Sensors
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PVDF is piezoelectric and the voltage induced
by bending PVDF films can be measured. The
surface of the PVDF is coated with metal to
allow electrical measurements.
PVDF is pyroelectric and readily absorbs
thermal radiation in the range 1000-1200 cm-1.
The voltage induced by exposing metalized
PVDF films to thermal radiation can be
measured.
By virtue of its piezoelectric properties PVDF
possibly could be fabricated into a surface
acoustic wave based sensing system.
Commercially available metal coated
piezoelectric PVDF sensor elements
Smart Sensors
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We use the term “Smart Sensor” to refer to systems that
employ a sensor interfaced to microelectronics. Here we
will use piezoelectric/pyroelectric PVDF films as our
sensors and a computer will take the place of the
microelectronics. The systems described are not
engineered to minimize size and power consumption but
clearly those would be goals in any widely deployed
practical device.
A USB data acquisition port will allow measured voltage
changes to be easily converted to computerized
information for data storage and analysis.
Circuits
Voltage Follower
Electronics
 TL082. Dual OpAmp
 Dual voltage source:
± 15V
Circuits
Electric Charge
Measurement
Electronics
 1: TL082. Dual OpAmp
 1: R 10 MΩ. 10 megaohms resistors
 1: 0.001 uF. 0.001 microfarads capacitor. 1 nF or
1 nano-farad
 Dual voltage source:
± 15V
Circuits
Differential Amplifier
Electronics
 TL082. Dual OpAmp
 3: R 10 MΩ. 10 megaohms resistors
 Dual voltage source:
± 15V
Deflection Sensor
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Two PVDF metal coated films mounted on
both sides of a flexible material.
The response of these films capable of
quantifying the magnitude, speed and
direction of the flexion movement.
Circuit (A) used to follow voltage changes
PVDF sensor elements,
detection circuit and USB data port
PVDF sensors mounted on a solid
substrate and interfaced to a detection
circuit
USB data port interfaced to laptop
computer gives system properties of
a “smart sensor”.
Output PVDF sensors on a ruler
undergoing oscillator flexing-Note polarity
(green/yellow). Blue represents the
combined output signal.
Output PVDF sensors on flexed rulerNote polarity (green/yellow) and
combined signal.
Plot of ln(Displacement) vs time showing that the
motion of the flexible material is described by the
equation D=D0 exp (-t/t); this equation
characterizes an under damped oscillator.
6
5
Ln(D)
4
3
LnI
Linear (LnI)
2
1
0
0
50
100
Time
150
200
Pyroelectric Matrix Array
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PVDF is pyroelectric and readily
absorbs radiation around 1000-1200
cm-1 .
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Four sensors in matrix array.
Array capable of quantifying the heat
intensity and the location of the heat
source.
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Four Panel Thermal Detection
Infrared Spectrum of PVDF taken on a Bruker IFS 66v spectrometer,
equipped with a DTGS detector and a KBr beamsplitter.
Note that the strong absorption around 1000 cm-1
Voltage output 4 panel Pyroelectric Sensor when
exposed to an asymmetrically located heat source
Future Work
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Mechanical and Thermal stabilization of
sensor platform.
Detailed analysis of experimental results
and development of effective learning
strategies based on PVDF sensors
Develop and understand mathematical –
electrical models
Use PVDF SAW devices in a chemical
sensor system.
Personal Acknowledgements
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
Dr. Tim Porter of the Physics and Astronomy
Department at Northern Arizona University
helped design a number of our detection
circuits.
Dr. Robert C. Hughes, Sandia National
Laboratories, provided important advice
during the early stages of this work.
Support Acknowledgement

This material is based upon work
supported in part by the U. S. Army
Research Laboratory and the U.S. Army
research Office under Contract
W911NF0410052.
Thank You for Your Attention