CNT-based-Thermal-convective-accelerometer
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Transcript CNT-based-Thermal-convective-accelerometer
CNT-BASED THERMAL CONVECTIVE ACCELEROMETER
Presented by Yu ZHANG. Supervised by Prof. Wen J. LI
OUTLINE
Introduction
Literature Review
Sensor Design
Test Setup
Test Results
Conclusion
2
INTRODUCTION
Literature Review
Sensor Design
Test Setup
3
INTRODUCTION
Background
The
method to align post grown Carbon-Nanotubes between
microelectrodes using dielectrophoretic (DEP) forces was developed in
CMNS. 2003
Experiments
showed CNT bundles can detect environmental temperature
change. 2004
When
heated within liquid, CNTs can generate thermal vapor bubble
around itself . 2007
4
INTRODUCTION
Idea
Acceleration/tilting will lead to deformation of the vapor bubble.
Temperature distribution around the bubble will change
If
other CNT bundles can be fabricated around the bubble, they can sense
the temperature change caused by acceleration.
5
INTRODUCTION
Aim of Research
Choose
applicable
principle, design
the structure
Review the
working principle
of thermal
motion sensor
Fabricate sensor
chips, build
prototypes
Purchase and set
up test
equipments
CNT-based
thermal
accelerometer
Test and
characterize
sensors’
response
6
Introduction
LITERATURE REVIEW
Sensor Design
Test Setup
Test Results
7
Motion Sensors
Thermal Motion Sensors
Carbon-Nanotube
Manipulation
Carbon-Nanotube
Sensors
LITERATURE REVIEW
Literature Review: Contents
8
Convert motion into electric
signal
LITERATURE REVIEW
Review of Motion Sensors
•Linear motion: accelerometer/inclinometer
•Angular motion: gyroscope
Application in industry, consumer electronics, input devices, instruments
•Inclination: automobile stability, platform stabilization
•Orientation: gesture recognition, inertial navigation, active control
•Vibration: active suspension system, machine noise detection
•Shock: air bag system, release systems, structure monitoring
9
Sensors
Piezoresistive
acceleration
Reference frame
y
deflection
piezoresistor
Damper
Spring
Proof mass
x
base (reference frame)
LITERATURE REVIEW
Conventional Motion
Piezoelectric
acceleration
Acceleration
deflection
piezoelectric
layer
Moving/bending
of solid structure
base (reference frame)
Capacitive
acceleration
Change of
detector output
Convert to
electric signal
C r
A
d
d
deflection
base (reference frame)
10
Cons
Easy to design and model
Rely
Standard IC process *
Good cost/performance ration
Fast response
Acceleration
on solid moving parts: proof
mass
Better
sensitivity requires bigger
proof mass
LITERATURE REVIEW
Pros
Fragile,
cannot measure large
acceleration (<20g)
Low shock survival rate
Move/bending
of solid structure
Change of
detector output
replacement
for this step?
Convert to
electric signal
* for surface micromachined sensors only
11
sensor
Details
Acceleration
Acceleration
will lead to forced
convection of liquid within sealed
chamber
Use
Convection of
liquid
flow sensors to detect the
flow speed caused by convection
LITERATURE REVIEW
Thermal convective motion
Change of
detector output
Convert to
electric signal
Figure from [6]
12
Anemometer
Power
Based on thermal phenomenon:
•Add local heat to fluid, measure
the resulting temperature
•Very small Reynolds Number
•Laminar flow heat transfer
•Three sensing methods
Flow
Q
heater/detector
Temp.
LITERATURE REVIEW
Micro Flow Sensors
Calorimetric flow sensor
Power
Flow
Q
detector1 heater detector2
ΔTemp.
Time-of-flight flow sensor
Power
Flow
Q
heater
detector
ΔTime
13
First reported in 1997
Research
LITERATURE REVIEW
Research on Thermal Convective Accelerometer
groups in Canada, US, France, Germany,
China.
Acceleration
Commercial products by MEMSIC. Inc.
Based
Convection of liquid
on integrated thermal flow sensor, to sense
convection caused by acceleration.
Up to two sensing axis
Thermal detector
Convert to electric signal
14
LITERATURE REVIEW
Working Principle
Temperature
a=0
a≠0
ΔT≠0
ΔT=0
detector1
One-axis Structure
sealed
chamber
heater
detector2
Two-axis Structure
Heater
detector 1
detector 2
Substrate
Figure from….
15
What are they?
Allotropes of carbon with a cylindrical nanostructure
Single-walled and Multi-walled
Synthesis
method: arc discharge, laser ablation, chemical
vapor deposition
LITERATURE REVIEW
Carbon-Nanotubes
CNT Integration
How to integrate?
Selectively grow on desired position
In situ CVD
Manipulate post-grew CNTs
Use AFM tips to move
Fluid friction
Dielectrophoretic (DEP) force
16
Mechanical sensors, chemical sensors, thermal sensors, pressure
sensors
LITERATURE REVIEW
Review of CNT Sensors
Sensing method:
•Raman spectrum shift
•Performance change as circuit elements
•Resonators
•Transistors
•Resistance change
•Deformation
•Temperature
•Chemical reaction
Possible for micro sensors
Reported by CMNS and other research groups
17
Literature Review: Conclusion
Build the sensor upon thermal convection sensing principle
Follow and improve the DEP manipulation method
Deposited CNT bundles work as Temperature Detectors
18
Introduction
Literature Review
SENSOR DESIGN
Test Setup
Test Results
Conclusion
19
Sensor Design: Contents
Important Questions
Mask Design
Fabrication
Sensor Prototyping
20
SENSOR DESIGN
Important Design Questions
Power
Project requirement consideration
Flow
•The structure should be DEP compatible
•Sensing structure:
•Anemometer
•Calorimetric structure
•Time-of-flight structure
Q
heater/detector
Temp.
Power
selected structure
Flow
Q
detector1 heater detector2
•No conditioning and feedback circuit
ΔTemp.
Power
MEMS structure consideration
•Thermal insulation
Flow
Q
heater
detector
ΔTime
21
SENSOR DESIGN
Thermal Insulation
Where to insulate (minimize heat flux)
•Between heater and detectors
•Between the sensing block and the substrate
Better thermal insulation leads to
•Higher heater temperature
•Better sensitivity
22
SENSOR DESIGN
Benefits of Thermal Insulation
flow
Q
substrate
flow
brings away
heat
heat from substrate
Better thermal
insulation
Minimize heat
capacitance of
the substrate
Tdetector
Rdetector
Tsubstrate > Tdetector
Reduce heat
flux from
substrate
Improve
sensitivity
23
SENSOR DESIGN
Bridge Structure
Etched Cavity
sensor
sensor
heater
Top view
sensing block
sensor
heater
sensor
Side view
substrate
substrate
Insulation Layer
Membrane
sensing
block
sensing
block
thermal insulation layer
substrate
substrate
Side view
membrane
24
Use glass as substrate
Good thermal insulation result
Fabrication process available
Simple structure
Need Cr layer to improve adhesion
Cannot integrate with IC
sensing
block
metal
adhesion layer
Glass substrate
Material
Silicon
Porous Silicon
Glass
Air
κ (W•m-1•K-1)
125
1.1*
1.2
0.025
* From Reference [12]
SENSOR DESIGN
Thermal Insulation Design
25
One pair of electrodes -> anemometer structure
•One CNT bundle as heater/detector
Three pairs of electrodes -> calorimetric
One 1-axis
calorimetric
structure
structure (1-axis)
SENSOR DESIGN
Sensor Chip Mask Design
•One CNT bundle as heater, two as detectors
Five pairs of electrodes -> calorimetric
structure (2-axis)
•One CNT bundle as heater, four as detectors
Three
anemometer
structure
Mask Layout
Sensing Block
26
Au
Cr
Substrate
STEP 1
SENSOR DESIGN
Sensor Chip Fabrication
Substrate
STEP 2
CNT bundle
Substrate
STEP 3
Protection layer
STEP
STEP 44
Substrate
27
SENSOR DESIGN
CNT Manipulation
Improved DEP Circuits
Multi-walled CNTs are used
Signal
Generator
Disperse MWNT into ethanol
Resistors
Separate bundles using ultrasonic
Gaps
detector 1
Drop 2μL above the electrodes
heater
Apply
8V peak-peak, 1MHz AC,
from signal generator
detector 2
Captured Microscope
detector 1
Image
100μm
CNTs
heater
a
detector 2
28
Sensor
chip
PDMS-Glass
Bonding
Mask for sensor
chip
PDMS
chamber
Stick to
PCB board
SENSOR DESIGN
Sensor Building Processes
Mask for PDMS
Wire boding to
PCB board
29
SENSOR DESIGN
Prototypes
Air
Ethanol
Air
Ethanol
30
Introduction
Literature Review
Sensor Design
TEST SETUP
Test Results
Conclusion
31
TEST SETUP
Source and Measure
Test Circuit
Use
Source & Measure Units
(SMUs) to power up and measure.
Keithley 2400 Sourcemeter: 1 SMU
Keithley 2600 Sourcemeter: 2 SMUs
linked together to
computer via GPIB
HI
Im
I
Vm
CNT
Sourcemeters
synchronized by
collected time stamps
SMU
LO
Sourcemeter data
Source meters
Constant current configuration
32
TEST SETUP
Vibration Exciter
a
Tilting Plate
spring
LO
HI
N
S
coil
spring
Test Setup
Test Setup
PC with
LabTracer®
GPIB-USB
Adaptor
GPIB
USB
Sensor
signal
generator
power
amplifier
Computer
Single-channel
Sourcemeter
Vibration
Exciter
Tilting-rotary
plate
laser
vibrometer
sensor
SMU
Dual-channel
Sourcemeter
33
Introduction
Literature Review
Sensor Design
Test Setup
TEST RESULTS
Conclusion
34
Thermal Sensing Test
TEST RESULTS
Test Results: Contents
Tilting Test
Vibration Test
35
0
Sensor1: T CR=-0.12%
Resistance Change ( R/R)
-0.01
Sensor2: T CR=-0.11%
TEST RESULTS
Thermal Sensitivity
-0.02
-0.03
-0.04
-0.05
-0.06
-0.07
20
30
40
50
60
70
Temperature ( C)
R R0 1 R TR T0
Tested in Climatic
Chamber. Fixed humidity.
Higher temperature -> Smaller resistance:
Negative TCR
36
TEST RESULTS
Self-heating Test
-3
3.5
Measure voltage
Ohm's Law prediction
15
x 10
3
failure point
Power (W)
Voltage (V)
2.5
10
2
1.5
safe bundary
1
5
0.5
0
0
0.5
1
1.5
Current (A)
2
2.5
3
-4
x 10
0
-8
10
-6
10
Current (A)
-4
10
37
TEST RESULTS
Temperature Change Caused by Heater
-3
2
x 10
Sensor 1
Sensor 2
Resistance Change (R/R)
0
Linear fit 1
Linear fit 2
-2
-4
-6
-8
-10
0
1
2
Heater Current (A)
3
-4
x 10
38
Proving Test
TEST RESULTS
Test Results: Contents
Tilting Test
Vibration Test
39
TEST RESULTS
Tilting Test
Tested on tilting plate
•Anemometer structure with air sealed: No response
•Anemometer structure with liquid sealed: No response
•Calorimetric structure with air sealed: No response
•Calorimetric structure with liquid sealed:
40
TEST RESULTS
Tilting Test
0.3
Detector1
Configuration
•Convection medium: ethanol
•Input power
•heater: 6μW
•detectors: 1nW each
Result
Change of Resistance (R/R)
0.2
•Two sensors give opposite
responses.
•Very good sensitivity.
•Very small power
consumption
•Liquid convection
medium
Conventional
thermal accelerometers:
Detector2
0.1
0
-0.1
-0.2
0
10
20
30
40
50
60
Tilting Degree (°)
70
80
90
0.2mW to 480mW*
*Table 2.2, Page 24, Thesis
41
Proving Test
TEST RESULTS
Test Results: Contents
Tilting Test
Vibration Test
42
TEST RESULTS
Vibration Exciter Calibration
Use laser vibrometer to measure velocity, then calculate acceleration
Fixed input power, varying input frequency.
Frequency limited by Sourcemeter sampling frequency
data
fit
Measured acceleration (m/s2)
1
0.1
0.01
y(x) = a x^n + c
a = 0.012068
c = -0.001069
n = 1.9357
1
2
3
4
Input frequency (Hz)
5
6
7
8 9 10
43
TEST RESULTS
Vibration Test Result
Test progress
•Anemometer structure with sealed air: yes
•Anemometer structure with sealed liquid: no
•Calorimetric structure: no
44
TEST RESULTS
Sensor Response to Vibration
Test mode: bias current 10nA
Power consumption:
P1 I 2 R1 10nA 106k 10.6 pW
2
P2 I 2 R2 10nA 39k 3.9 pW
2
45
1
0.9
Response (Percentage Amplitute)
0.8
Frequency fixed to 2Hz
Sourcemeter current lower range
0.7
0.6
Input current: 10pA to 0.1mA
0.5
Response defined by
0.4
0.3
Current used in test (10nA)
Rmax Rmin
R
0.2
0.1
0
-11
10
TEST RESULTS
Sensor Response Under Different Heating Current
-10
10
-9
10
-8
-7
10
10
Input Current (A)
-6
10
-5
10
-4
10
1.8
In tests, driven current was set to
10nA
1.6
Response (Percentage Amplitute)
1.4
Sourcemeter current lower range
1.2
1
0.8
0.6
Current used in test (10nA)
0.4
0.2
0
-11
10
-10
10
-9
10
-8
-7
10
10
Input Current (A)
-6
10
-5
10
-4
10
46
TEST RESULTS
Acceleration Responsivity
13000
12000
Sensor R ( )
11000
10000
9000
8000
More
sensitive
acceleration
7000
to
small
6000
0
0.2
0.4
0.6
0.8
1
1.2
Acceleration peak (m/s 2)
Linear – log relationship
Saturation limit
7000
> 1.2m/s2
Sensor R ( )
6000
5000
4000
3000
2000
0
0.2
0.4
0.6
0.8
Acceleration peak (m/s 2)
1
1.2
47
4
x 10
2.85
1.5
1.25
1
2.74
velocity
0.5
2.63
0.25
0
-0.25
2.52
-0.5
Acceleration (mm/s2)
Sensor Resistace ( )
0.75
a=dv/dt
R=vi
Dual channel
Sourcemeter
voltage
output
-0.75
2.41
-1
-1.25
2.3
2
3
4
5
6
7
8
Time (second)
9
10
11
Laser
Vibrometer
TEST RESULTS
Phase Delay Test
Sensor
-1.5
12
4
x 10
1.5
1.25
11
0.75
10.5
0.5
10
0.25
0
9.5
-0.25
-0.5
9
Acceleration (mm/s2)
Sensor Resistance ( )
1
180°
phase delay
Response time not detectable
-0.75
-1
8.5
-1.25
8
2
3
4
5
6
7
8
Time (second)
9
10
11
-1.5
12
48
Introduction
Literature Review
Sensor Design
Test Setup
Test Results
CONCLUSION
49
CONCLUSION
Conclusion – Work Done
Working
principle, structures and performances of currently developed
thermal convective accelerometers were reviewed.
CNT-based
thermal convective accelerometers were designed and
prototyped.
Testing facilities
were purchased and set up.
Prototypes were tested under inclination and vibration.
50
Calorimetric
CONCLUSION
Conclusion - Results
structure with sealed ethanol can sense static inclination
Anemometer structure with sealed air can sense vibration
Contributions
•First CNT based motion sensor
•First CNT based thermal convective motion sensor
•Smallest power consumption *
•No solid proof mass, easy to fabricate
•More understanding about heating and sensing effect of CNTs
* Considering the sensing block only
51
52
SUPPORTING MATERIALS
53
SUPPLEMENTS
Improving Frequency Test Range
0.001Hz
sourcemeter
sampling limit
vibration exciter
working range
0.1Hz
10Hz
1Hz
crank-link mechanism
100Hz
1000Hz
vibration exciter
New circuit
sampling limit
0.001Hz
0.1Hz
1Hz
10Hz
100Hz
1000Hz
54
SUPPLEMENTS
Crank-link Mechanism
motor
controller
power
amplifier
Computer
sensor
SMU
55
SUPPLEMENTS
Sensor Read-out Circuit
+
-
I
Vm
CNT
Im
CNT
R3
+
Rg
+
SMU
R2
R1
R1
R2
Instrumentation amplifier
Rf
C
ADC
R3
Filter
56
SUPPLEMENTS
Future work – Sensor Charactorizaiton
Step response
Bandwidth (frequency response)
Saturation (requires higher acceleration peak)
57
Future Work – Sensor Design
Size of sealed chamber
Noise level
Optimized input current (sensitivity
Properties
and noise)
of convection medium (liquid, air, pressure)
Compensation of environmental temperature change
Feedback control
58