This is an initial presentation of my Senior Design project that my group an i completed at the end of our senior year at Drexel University. The device we designed and created tests skin to determine its thickness and elasticity. This device can be used to monitor skin again as well as various other skin diseases and cancers. Team Members: Brandon Bachert, Joseph Erthal, Tony John & Kristen Smith Advisor: Dr. Wan Y. Shih1, Dr. Wei-Heng Shih

1. Team 3 Brandon Bachert 1 , Joseph Erthal 1 , Tony John 1 & Kristen Smith 1 Advisor: Dr. Wan Y. Shih 1, Dr. Wei-Heng Shih 2, 1 Biomedical Engineering, Drexel University 2 Materials Science and Engineering, Drexel University Simultaneous Determination of Elastic Modulus and Thickness of Skin with Piezoelectric Fingers

3. Introduction to Skin & its Properties (http://www.clarian.org/ADAM/doc/graphics/images/en/8912.jpg) Skin Fat Young's Modulus of skin 420 kPa-850 kPa Thickness of skin 0.5 mm–1.1 mm Young's Modulus of fat ~10 kPa

7. Testing Criteria - Phantom Top “Skin” Layer Eskin = 420-850 kPa Bottom “Fat” Layer Efat = 3-10 kPa 0.5-1.1 mm >1.0 mm (Hendriks) Wire Probe Cantilever

8. OUR SOLUTION

9. Cantilever Design (Side-view) Driving PZT Sensing PZT Stainless Steel Wire Probe Clamp Clamp 20 mm 12 mm 127 microns 127 microns 50 microns Sample

10. Probe Size (Yegingil 2007) Skin Fat Probing Depth = 2*D Diameter = D 2.1 mm 1 mm Probe Diameter Depth Sensitivity 2 x Diameter (mm) Cantilever A 0.60 1.12 Cantilever B 0.71 1.42 Cantilever C 0.91 1.83

11. THEORY

12. Theory (Springs in Series) Layer 1 Layer 2 (Yegingil et al. 2007)

13. Known and Unknown Values E A E skin E fat T skin D A -T skin D A E B E skin E fat T skin D B -T skin D B E C E skin E fat T skin D C -T skin D C

14. Calculations to determine Elastic Modulus of Sample

15. Max Cantilever Spring Constant To achieve 10% strain for patient comfort and meet our constraint to design for use on humans.

17. Prototype (1 of 3 cantilevers pictured)

18. Measuring Spring Constant (k) Mass (g) Force = mg (N x 10 -04 ) Weight 1 0.0323 3.17 Weight 2 0.0828 8.12 Weight 3 0.1395 13.7 Weight 4 0.1931 18.9 Weight 5 0.2703 26.5

20. Spring Constant Results Measured Cantilever Spring Constants Spring Constant (k) 3 Trials Std Dev of 3 Trials (+/-) Cantilever A 107 N/m 0.8% Cantilever B 115 N/m 2.9% Cantilever C 101 N/m 0.4%

21. Testing Criteria - Phantom Design Top “Skin” Layer Material: Versaflex Rubber Eskin = about 500 kPa Bottom “Fat” Layer Material: Lab Gelatin Efat = 3-10 kPa 1.0 mm >1.0 mm (Hendriks) Wire Probe Cantilever

22. Cutting Versaflex 1mm Thickness with Diamond Saw Results 1.03 ± 0.08mm Versaflex Sample Diamond Saw Blade Glass Slide

23. Phantom Versaflex Rubber Gelatin Petri Dish Versaflex 1(mm) Petri Dish Gelatin (1mm)

24. Experimental Setup DC Power Supply O-scope Applied Voltage Induced Voltage Laser Displacement Meter 0.0000 mm

25. Experimental Setup Laser Displacement Meter Sample Induced Voltage Ground Applied Voltage Cantilever

26. Indentation Test

27. Sample Data One Cantilever- Versaflex

28. Determining Effective Modulus V(induced w/sample) (Volts) E eff A= circular contact area K= Cantilever spring constant v= Poisson’s Ratio=0.5 (Yegingil et al. 2007)

30. Calculation of Young’s Modulus Using Displacement

31. Results: E of Gelatin = 5.6 kPa Meets Criteria Measuring E in range of Fat Gelatin (5mm) Petri Dish

32. Results: E of Versaflex = 354 kPa Does Not Meet Criteria for Measuring E in Range of Skin Versaflex (5mm) Petri Dish

33. Results: E of Gelatin on Versaflex = 9.6 kPa Inverse Configuration of Skin) - 20% Error Versaflex (5mm) Petri Dish Gelatin (1mm)

34. Testing the Phantom Versaflex Rubber Gelatin Petri Dish

35. Results: E of Skin Phantom Phantom Trial 1 Phantom Trial 2 Expected/ Theoretical Cantilever A E A (kPa) 61 190 81 Cantilever B E B (kPa) 160 410 32 Cantilever C E C (kPa) 210 330 21

36. Testing Effect of Petri Dish Versaflex on Plastic (>500kPa Expected) Versaflex on 5mm Gelatin Expected/ Theoretical Cantilever A E A (kPa) 87 130 81 Cantilever B E B (kPa) 25 64 32 Cantilever C E C (kPa) 40 120 21 Versaflex (1mm) Petri Dish Gelatin (5mm) Versaflex (1mm) Petri Dish

37. Testing effect of Cantilever Placement “ 0” Position “ -100 microns” “ -200 microns” “ -300 microns” “ -400 microns” “ -500 microns” “ -300 microns” trial 2 “ -400 microns” trial 2 Cantilever A E A (kPa) 19 23 13 1200 1200 --- 1200 --- Cantilever B E B (kPa) 230 470 650 770 1000 1000 --- 1000 Cantilever C E C (kPa) 290 400 560 610 800 800 --- 800

39. Conclusions Little/No Resistance From Sample Small Difference between Slope with and without Sample Large Resistance From Sample Big Difference between Slope with and without Sample

42. Budget

43. Competitive Matrix Piezoelectric Cantilever DermCup 2020® Echo-rheometer J&J Photo-technique Tensometer Low Price Yes No No No No Skin Layer differentiation Yes No No No No Quantitatively measures skin thickness Yes Yes No No No Quantitatively Measures Elastic Modulus Yes No Yes No Yes Small Portable Size Yes No No Yes No

44. Research and Development

45. Product Launch

46. Economic Analysis

50. Schedule Key Completed In Progress To be completed Fall 2008 Task Wk1 Wk2 Wk3 Wk4 Wk5 Wk6 Wk7 Wk8 Wk9 Wk10 Wk11 BREAK Work on proposed biorhythm device Research (ongoing) - PZT properties, applications, cantilever properties, skin thickness & elasticity, etc. Brainstorm, develop and revise Problem Statement, Constraints, and Criteria Discuss feasibility and alternative solutions with advisor Online lab safety - Acquire key from Dr. Knight Calculate theoretical values of PZT and Stainless steel to achieve theoretical K value in the range we have specified Practice work with cantilevers and materials (cutting, gluing, and sanding materials as they are fragile and crack easily) Build several cantilever (cut materials to proper dimensions, glue layers together, sand cantilever) Order clamps and probes from Machine Shop Check impedance of cantilevers to be within a certain range

51. Schedule Winter 2009 Task Wk1 Wk2 Wk3 Wk4 Wk5 Wk6 Wk7 Wk8 Wk9 Wk10 Meet with advisor Clarify calculations Discuss limitations discovered this far Develop Probes (Probes from machine shop were wrong size) Continue building cantilevers Check impedance of cantilevers Attach probes to cantilevers Insert cantilever into clamp Solder wires to cantilever Test K value using method involving resistance to force from stainless steel cantilever Test K value using weights method Build/Develop skin model Initial testing of prototype using skin model Make adjustments on final cantilever prototype Spring 2009 Task Wk1 Wk2 Wk3 Wk4 Wk5 Wk6 Wk7 Wk8 Wk9 Wk10 Final cantilever prototype testing on gelatin and skin model Analyze results from LabView Testing `

52. Thank You Dr. Wan Shih, Dr. Wei-Heng Shih, Josa Hanzlik, Xiatong Gao, Dr. Karen Moxon, Dr. Elisabeth Papazaglou and Dr. Ken Barbee for all of your help. Acknowledgements

53. QUESTIONS???