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Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring...

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Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan (Mechanical Engineering) Sai Ma (Biomedical Engineering)
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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.

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)

Page 2: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 3: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 4: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Amplifier A/D Converter

MicrocontrollerMSP430 Launchpad

TX

RX at hospital

Encoding

Sampling

Signals from sensors

ANT

Temperature

Pressure

Attachment

Moisture

Disposable Reusable

Page 5: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 6: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

TEMPERATURE

Page 7: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 8: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 9: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 10: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

PRESSURE

Page 11: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Diaphragm Based Pressure Sensor

Bend due to differential pressure can be measured as a change in capacitance

Page 12: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Trivial Fabrication

PDMS

Page 13: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 14: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 15: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 16: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Δ𝑐 (𝑃 )≅𝜖 𝐴 8

15𝑃 𝑎4

64 𝐷𝑑

=ℂ1𝑃

Assuming that:

𝑃

Δ𝑐 (𝑃 )

Slope =

Page 17: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

TESTING THE SENSORS

Page 18: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Testing

CAPACITIVE SENSOR

(TENMA 72-1025)

Page 19: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 20: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 21: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

ATTACHMENT/MOISTURE

Page 22: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 23: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 24: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Decouple with a hydrophobic layer

Attachment Moisture/Bandage Viability

Paper/ Bandage

Wax

Electrodes

Gauze

Electrodes

Page 25: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 26: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

INCORPORATION TEMP AND ATTACHMENT

Page 27: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 28: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 29: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 30: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Screen Printing

Page 31: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Screen Printing

Page 32: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Screen Printing

Page 33: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Screen Printing

Page 34: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 35: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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

Page 36: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

DEMONSTRATION

Page 37: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Thanks for listening!

• Special thanks to:

• Dr. Agah• Diana Nakkide• ICTAS building• Kris Dixon• Elizabeth Elvington

Page 38: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

Attachment/Bandage Viability Measurements

From Agilent 34401A manual

Page 39: Paper Based Partially Disposable MEMS Smart Bandage Presented to the MEMS Fab to App class Spring 2013 By: Lisa Anders (Electrical Engineering) Vivek Jayabalan.

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.

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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