paper based partially disposable mems smart bandage presented to the mems fab to app class spring...
TRANSCRIPT
![Page 1: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan](https://reader036.vdocuments.net/reader036/viewer/2022062409/56649f335503460f94c4f236/html5/thumbnails/1.jpg)
Paper Based Partially Disposable MEMS Smart Bandage
Presented to the MEMS Fab to App class Spring 2013By:
Lisa Anders (Electrical Engineering) Vivek Jayabalan (Mechanical Engineering)Sai Ma (Biomedical Engineering)
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Healthcare-Associated Infection Rates
4.5 HAI’s for
every 100 hospital admissions annually
1,737,125
cases of Infection
290,485Surgical site infection
COST OF $35.7-45.0 billion
70%
$25.0-31.5 billion
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The goal is to create a "smart" bandage that would
incorporate an inexpensive modular sensing platform for
monitoring healing including temperature, pressure,
attachment, and bandage viability using an active
electronics design.
Objective
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Amplifier A/D Converter
MicrocontrollerMSP430 Launchpad
TX
RX at hospital
Encoding
Sampling
Signals from sensors
ANT
Temperature
Pressure
Attachment
Moisture
Disposable Reusable
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Temperature Pressure
AttachmentMoisture
Sensors intended to be incorporatedinfection symptom
monitor bandage attachment
Bandage viability, want dry environment to prevent infection
monitor person movement, self-care
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TEMPERATURE
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Skin Temperature & Infection
Temperature difference between periwound skin and an equivalent contralateral control site was found to be less than 2°C.If infection is present, the difference is greater than 2°C
On average, the day one skin temperature at the hottest spot on the affected limb was 34.4 degrees C, compared with 30.9 on the unaffected limb.
http://http://ovidsp.tx.ovid.com
increase2 °C
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Temperature sensing theoryThermocouple:
Two dissimilar conductors in contactwhich produce a voltage when heatedConvert a temperature into electricity
Type T (copper – constantan) thermocoupleRange: -250-300°C)Sensitivity: 43 µV/°CSkin temp: 32-37°C
Unsheathed fine gage T type thermocouple(0.025mm to 0.81mm)
Choose 0.125 mm for prototype
http://hypertextbook.com/facts/2001/AbantyFarzana.shtml
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Temperature calibration
15 20 25 30 35 40 45 50 55
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
1.00
1.20
f(x) = 0.0409785714285714 x − 1.01910714285714R² = 0.999851540443336
Chart Title
Temperature (C)Vo
ltag
e (m
V)
34 35 36 37 38 39 40 410.35
0.40
0.45
0.50
0.55
0.60
0.65
f(x) = 0.0390857142857 x − 0.9527142857143R² = 0.999724350139427
Chart Title
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PRESSURE
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Diaphragm Based Pressure Sensor
Bend due to differential pressure can be measured as a change in capacitance
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Trivial Fabrication
PDMS
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Modelling Pressure Sensors
𝑤 (𝑟 )= 𝑃 𝑎4
64 𝐷 [1−( 𝑟𝑎 )2]2
𝐷= 𝐸h3
12 (1−𝜈2 )
is the deflection at a particular radius is the pressure is the Radius of the plate and is its thickness is the Young’s modulus and is the Poisson's ratio
[1]
[2]
[2]
[1] Eaton, William P., and James H. Smith. "Micromachined pressure sensors: review and recent developments." Smart Materials and Structures 6.5 (1997): 530.[2] Young, Warren C., and Richard G. Budynas. Roark's formulas for stress and strain. Vol. 6. New York: McGraw-Hill, 2002.
Applied Pressure
Reference Pressure
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Change in capacitance
𝐶=𝜖 𝐴
𝑑−𝑤 ′
is the Average Displacement
𝑤′=1𝑎∫0
𝑎𝑃 𝑎4
64𝐷 [1−( 𝑟𝑎 )2]2
𝑑𝑟
¿ 815
𝑃 𝑎4
64𝐷
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Pressure v/s Δ Capacitance
𝑐 (𝑃 )=𝜖 𝐴
𝑑− 815
𝑃 𝑎4
64𝐷
-
Δ𝑐 (𝑃 )=𝜖 𝐴 8
15𝑃 𝑎4
64𝐷
𝑑− 815
𝑃 𝑎4
64𝐷
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Δ𝑐 (𝑃 )≅𝜖 𝐴 8
15𝑃 𝑎4
64 𝐷𝑑
=ℂ1𝑃
Assuming that:
𝑃
Δ𝑐 (𝑃 )
Slope =
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TESTING THE SENSORS
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Testing
CAPACITIVE SENSOR
(TENMA 72-1025)
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Results
No of BoltsWeight (in gm)
Average Change(in pF)
5 26.09 1.58677 33.23 1.6967
10 43.85 2.2717 68.73 3.3733
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Conclusion
• Established that we can build simple paper based pressure sensors, that responds to pressure changes
CHALLENGES• Non-Linear• Sensitive Equipment• Elaborate Calibration
POTENTIAL• Inexpensive• Sensitive • Easy Fabrication• Other than Electronics,
requires no instruments
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ATTACHMENT/MOISTURE
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Skin resistance
• Nonhomogenous: connective tissue, blood vessels, nerve cells. • Resistance varies based on skin layer, thickness, skin hydration,
electrode size and geometry• At low frequencies current goes around cells
From Bioimpedance and Bioelectricity, 2008Skin image from http://klimadeodorant.com/skin1/images/custom/pages/skin.jpg
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Switch approach for measuring attachment
0.5 1 1.5 2 2.5 3 3.50
5
10
15
20
25
30
35
40
45
50
Position versus Resistance
Across pinkie finger Mohm Across pointer finger MohmAcross arm Mohm
Distance between electrodes (cm)
Resis
tanc
e (M
ohm
s)
At 10 kHz
From Bioimpedance and Bioelectricity, 2008
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Decouple with a hydrophobic layer
Attachment Moisture/Bandage Viability
Paper/ Bandage
Wax
Electrodes
Gauze
Electrodes
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Theoretical fluid values:
Resistance of paper doped with fluid
Blood 0.7 S/m-> 0.49 ohmsConductivity of DI and tap water from: http://www.mbhes.com/conductivity_measurement.htm
DI Tap PBS0
0.5
1
1.5
2
2.5
3
3.5
2.86 2.45 0.074
Liquid type
Resis
tanc
e (M
ohm
s)
From Bioimpedance and Bioelectricity, 2008
70 kohms 1.4 ohms 0.05 ohms
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INCORPORATION TEMP AND ATTACHMENT
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Testing temperature of 3 people
Lower arm Middle arm Upper arm2526272829303132333435
Temperature vs. Position
Tem
pera
ture
/ °C
Lower arm Middle arm Upper arm25
26
27
28
29
30
31
32
33
34
Lisa Sai Vivek
Tem
pera
ture
/ °C
Temperature measurementDirectly on skin
Temperature measurementThin gauze barrier
Thin gauze barrier seems decreases the measured temperature a bit
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Individual variation supports “switch” approach
inside w
rist
forearm
inside elbow
elbowbice
ptri
cep
0.01
0.1
1
10
100
Day 2
Lisa Sai Vivek
inside w
rist
forearm
inside elbow
elbowbice
ptri
cep
0.01
0.1
1
10
100
Day 1
Resi
stan
ce (M
ohm
s)
90 Mohms
.7 Mohms
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Price can be reduced through a bulk fabrication process
• Thermocouple: $ 3.600• 1 piece of filter paper: $.0649• 9 cm conductive tape: $1.032• Gauze: $0.442• Wax: $0.19
• Total: $5.3289
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Screen Printing
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Screen Printing
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Screen Printing
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Screen Printing
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Future Work
• Microcontroller and ANT incorporation– MSP430- ultra low power– ANT- ultra low power, +95dB,
• Unobtrusive and discreet• Screen printed electrodes• Further safety studies• More sensors!– Pressure sensor– pH Sensor
Ti.com
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Conclusion
• Successfully designed, built, and tested a Smart Bandage prototype
• Interdisciplinary project between ECE, ME, and BMES• Shows promise to improve healthcare conditions and
patient recovery
Images from: http://coachmunro.com/wp-content/uploads/2011/05/band_aid-2830.jpg,http://rashaba.com/net/file/pic/photo/03afdbd66e7929b125f8597834fa83a4_500.png
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DEMONSTRATION
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Thanks for listening!
• Special thanks to:
• Dr. Agah• Diana Nakkide• ICTAS building• Kris Dixon• Elizabeth Elvington
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Attachment/Bandage Viability Measurements
From Agilent 34401A manual
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Testing temperature of 3 people over 2 days
Lower arm Middle arm Upper arm2526272829303132333435
Temperature vs. Position
Tem
pera
ture
/ °C
Lower arm Middle arm Upper arm25
26
27
28
29
30
31
32
33
34
Lisa Sai Vivek
Tem
pera
ture
/ °C
Temperature measurementDirectly on skin
Temperature measurementThin gauze barrier
Thin gauze barrier seems decreases the measured temperature a bit
![Page 40: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan](https://reader036.vdocuments.net/reader036/viewer/2022062409/56649f335503460f94c4f236/html5/thumbnails/40.jpg)
Individual variation supports “switch” approach
inside w
rist
forearm
inside elbow
elbowbice
ptri
cep
0.01
0.1
1
10
100
Day 2
Lisa Sai Vivek
inside w
rist
forearm
inside elbow
elbowbice
ptri
cep
0.01
0.1
1
10
100
Day 1
Resi
stan
ce (M
ohm
s)
90 Mohms
.7 Mohms