effects_s
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effects_sTRANSCRIPT
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Control Engineering Laboratory
Energy Transformation EffectsIntroduction to Micro System Technology
Lecture 3
Quan Zhou
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Table of Contents, Slide 2
Energy Transformation Effects Mechanical
Piezoelectric Piezoresistive Electrostatic Electrorheological
Magnetic Hall Magnetoresistive Magnetostrictive Magnetorheological Magnetic shape memory
Thermal Seebeck effect Pyroelectric effect Thermo resistive effect Thermo elastic effect Shape memory effect Peltier effect
Radiation photoemissive photoconductive photovoltaic
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Table of Contents, Slide 3
Mechanical Effects
Piezoelectric Piezoresistive Electrostatic Electrorheological
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Table of Contents, Slide 4
Piezoelectric effect
Some crystals develop an electrical charge when they undergo a mechanical stress
Conversely, the application of an electric field to a piezoelectric crystal leads to a physical deformation
Piezo elements by PIPiezoelectric buzzers in alarm devices
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Table of Contents, Slide 5
Piezoelectric effect ...
First discovered by the Curie brothers in 1880 First applications with natural crystals in 1920s In the 1950s piezoelectric ceramics (PZT)
Piezoelectric ceramics must undergo a polarizing process for thepiezoelectric phenomenon to occur
Crystal structure must be asymmetric
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Table of Contents, Slide 6
Piezoelectric elementary cells
Above Curie temperature Below Curie temperature
PbZrO3-PbTiO3
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Table of Contents, Slide 7
Piezoelectric ceramics
As macroscopic point of view, molecular dipoles align within small areas forming large dipole moments
The domains are randomly oriented and therefore the net externalelectric dipole is zero
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Table of Contents, Slide 8
Piezoelectric ceramics...
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Table of Contents, Slide 9
Piezoelectricity models
Linear model
Neglects hysteresisEdTD
dETsST
E
+=+= S is strain tensor
T is stress tensor
E is the electric field vector
D is electric displacement vector
sE is the elastic compliance matrix when subjected to a constant electric field
d is a matrix of piezoelectric constants
eT is the permittivity measured at constant stress
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Table of Contents, Slide 10
Piezoresistive effect
In piezoresistive effect the relative change in resistance is proportional to the mechanical stress.
Utilized in many mechanical microsensors, such as pressure and acceleration sensors
Pressure sensors by Sensonor asa
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Table of Contents, Slide 11
Electrostatic effect
Origin lies in the Coulombic force, i.e. the attractive force between two conductive plates having opposite charges
When a voltage is applied between the plates, the attractive force FN is exerted on the plates
2
21
=
dUeAFN
-e -e -e
+e +e +e
FN
FN
d U
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Table of Contents, Slide 12
Electrostatic effect...
When a force is applied to a conductive plate, capacitance between the plates changes
Applications in microsensors, especially in force, pressure and acceleration sensors
Delft university of Tech.
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Table of Contents, Slide 13
Electrostrictive Effect
Electrostriction refers to deformation of the material when exposed to an electric field.
Similar to piezoelectric, occurs in ferroelectric materials Does not need asymmetric crystal structure Greater hysteresis Temperature dependent
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Table of Contents, Slide 14
Electrorheological effect
Electrorheological fluids can change state from liquid to solid when an electric field is applied
Discovered by Willis M. Winslow in the 1940s (Winslow fluids) Depending on the strength of the electric fluid, the ER fluid acts like
water or honey ER fluids consist of micro-sized particles suspended in non-
conducting liquid
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Table of Contents, Slide 15
Electrorheological effect ...
Electric field:1000 v / mm
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Table of Contents, Slide 16
Magnetic Effects
Hall Magnetoresistive Magnetostrictive Magnetorheological Magnetic shape memory
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Table of Contents, Slide 17
Hall effect
Based on Lorentz force
Utilized in Hall sensors
)( BvF = e
EHy = vxBz
VH = EHyw
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Table of Contents, Slide 18
Magnetoresistive effect
Resistance of a semiconductor changes in the presence of magnetic field
Based on the Lorentz force The deflection of the current paths leads to an increase in the
resistance of the semiconductor
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Table of Contents, Slide 19
Magnetostrictive Effect
Magnetostriction refers to magnetically induced shape change in ferromagnetic materials (Joule Effect)
Villari effect is a change in magnetization state due to a mechanical stress
Tohoku University
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Table of Contents, Slide 20
Magnetorheological effect
The flow rate of magneto-rheological fluids may be varied by the application of a magnetic field
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Table of Contents, Slide 21
Magnetic Shape Memory
Change of dimension, shape or stress due to an applied magnetic field
Finnish innovation (AdaptaMat Oy) Properties
large strain (4.5%) fast response (even up to 10 kHz) high power density (10 kW/Kg) Efficiency 10 - 20 %
00.5
11.5
22.5
33.5
44.5
Strain (%)
Electr
ostric
tors
Terfe
nol-D PZ
TMS
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Table of Contents, Slide 22
Thermal Effects
Seebeck effect Peltier effect Pyroelectric effect Thermoresistive effect Thermoelastic effect Shape memory effect
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Table of Contents, Slide 23
Seebeck effect A circuit consisting of two different
materials has different temperatures at sensing and reference junctions
Current flow between the junctions Discovered in 1822 by an Estonian
physician named Thomas Seebeck
Thermocouple
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Table of Contents, Slide 24
Peltier effect
Reversible to the Seebeck effect A current applied to an electric
circuit made of two dissimilar materials, results in either cooling or heating effect
Utilized in thermoelectric heating and cooling systems
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Table of Contents, Slide 25
Pyroelectric Effect
Pyroelectricity is the variation of electric charges on the surface of a polarized crystal when it is heated
increase in temperature increases output voltage
All pytoelectric materials are piezoelectric, but the converse is not true
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Table of Contents, Slide 26
Thermoresistive and Thermoelastic Effects
Thermoresistivity refers to variation of electrical resistance of metals and semiconductors with temperature
Thermoelastic effect refers to the thermal expansion of the material Volume change
Heated Cooled
MemsPI
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Table of Contents, Slide 27
Shape memory effect
Shape Memory Alloys (SMAs) are metallic materials that have an ability to remember their original shapes
Discovered in 1950s
Widely used Nickel-titanium (NiTi) alloys were found in the beginning of 1960s
Eyeglass frames by Marchon
NiTi spring is trained to open a valve and release hot water at the proper temperature, by Carioca
NiTi surgical tools: Precise bending of the tool to the proper shape in open heart surgery. The original shape returns upon heating during sterilization.
by St. Jude Medical
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Table of Contents, Slide 28
Shape memory effect ...
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Table of Contents, Slide 29
Shape memory effect ...
Stre
ss
Strain
Martensite
Austenite
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Table of Contents, Slide 30
Radiation Effects
Photoelectric effects photoemissive (radiation striking the prepared surface of a metal emits
electrons from the surface into space) photoconductive (light striking the photoconductive material reduces its
resistance) photovoltaic (when radiation is applied to a semiconductor sheet, photons
make electrons flow in one direction across a junction, generating a voltage, used in photodiodes and solar cells)