Paper Based Partially Disposable MEMS Smart Bandage

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

2. Healthcare-Associated Infection Rates 1,737,125 cases of Infection 4.5 HAI’s for every 100 hospital admissions annually 290,485 Surgical site infection COST OF $35.7-45.0 billion $25.0-31.5 billion

3. Objective 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 viabilityusing an active electronics design.

4. Signals from sensors Microcontroller MSP430 Launchpad Pressure Sampling Temperature Amplifier A/D Converter Attachment Encoding Moisture ANT TX Disposable Reusable RX at hospital

5. Sensors intended to be incorporated infection symptom monitor person movement, self-care monitor bandage attachment Bandage viability, want dry environment to prevent infection

6. Temperature

7. Skin Temperature & Infection increase 2 °C 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

8. Temperature sensing theory Thermocouple: Two dissimilar conductors in contact which produce a voltage when heated Convert a temperature into electricity Type T (copper – constantan) thermocouple Range: -250-300°C) Sensitivity: 43 µV/°C Skin 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

9. Temperature calibration

10. Pressure

11. Diaphragm Based Pressure Sensor Bend due to differential pressure can be measured as a change in capacitance

12. Trivial Fabrication PDMS

13. Modelling Pressure Sensors [2] [2] [1] Applied Pressure 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 Reference Pressure [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.

14. Change in capacitance is the Average Displacement

15. Pressure v/s Δ Capacitance • -

16. Assuming that: Slope =

17. TESTING THE SENSORS

18. Testing CAPACITIVE SENSOR (TENMA 72-1025)

19. Results

20. Conclusion • Established that we can build simple paper based pressure sensors, that responds to pressure changes • POTENTIAL • Inexpensive • Sensitive • Easy Fabrication • Other than Electronics, requires no instruments • CHALLENGES • Non-Linear • Sensitive Equipment • Elaborate Calibration

21. Attachment/moisture

22. 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, 2008 Skin image from http://klimadeodorant.com/skin1/images/custom/pages/skin.jpg

23. Switch approach for measuring attachment At 10 kHz From Bioimpedance and Bioelectricity, 2008

24. Decouple with a hydrophobic layer Attachment Moisture/Bandage Viability Electrodes Paper/ Bandage Gauze Wax Electrodes

25. Resistance of paper doped with fluid Theoretical fluid values: Blood 0.7 S/m-> 0.49 ohms 70 kohms 1.4 ohms 0.05 ohms From Bioimpedance and Bioelectricity, 2008 Conductivity of DI and tap water from: http://www.mbhes.com/conductivity_measurement.htm

26. Incorporation Temp and Attachment

27. Testing temperature of 3 people Temperature measurement Directly on skin Temperature measurement Thin gauze barrier Thin gauze barrier seems decreases the measured temperature a bit

28. Individual variation supports “switch” approach 90 Mohms .7 Mohms

29. 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

30. Screen Printing

31. Screen Printing

32. Screen Printing

33. Screen Printing

34. 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

35. 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

36. Demonstration

37. Thanks for listening! • Special thanks to: • Dr. Agah • Diana Nakkide • ICTAS building • Kris Dixon • Elizabeth Elvington

38. Attachment/Bandage Viability Measurements From Agilent 34401A manual

39. Testing temperature of 3 people over 2 days Temperature measurement Directly on skin Temperature measurement Thin gauze barrier Thin gauze barrier seems decreases the measured temperature a bit

40. Individual variation supports “switch” approach 90 Mohms .7 Mohms