Senior Design

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

Problem Statement Effects of Aging: $5.8 billion spent annually on anti-aging products as of 2008 Quantitative measurements Provide customers with a fair and unbiased assessment of their effectiveness (Global Industry Analysts, 2009) Young’s Modulus (kPa) Thickness (mm) Under 30 years 420 0.5-1.1 Over 30 years 850 Decreases by 0.2 - 0.3 % Change 15% 34%

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

Current Methods DermCup 2020® only measures skin thickness Echorheometer only measures elastic modulus Tensometer only measures elastic modulus J&J Photography technique qualitative test

Criteria Device must measure: Device must see changes produced by supplements such as Dermavite ™ (Thom 2005) Young's Modulus accuracy 7.5% Thickness accuracy 17% Skin Young's Modulus 420 kPa-850 kPa Thickness of skin 0.5 mm–1.1 mm Fat Young's Modulus ~10 kPa

Constraints Area of Advisor expertise Self Exciting, Self Sesning, Piezoelectric Cantilevers Available equipment Voltage source Oscilloscope Laser Displacement Meter Must be designed for eventual use on humans PZT Steel

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

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

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

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

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

Calculations to determine Elastic Modulus of Sample

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

Estimating Cantilever Dimensions Used published cantilever dimensions and k values (Yegingil 2007) to estimate E of cantilevers. Length (mm) Estimated Driving PZT Sensing PZT Desired Width (mm) Desired Spring Constant (N/m) E from Yegingil Cantilevers (Pa) 20 12 2 100 5.7 x 10 7

Prototype (1 of 3 cantilevers pictured)

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

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%

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

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

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

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

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

Sample Data One Cantilever- Versaflex

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)

Monitoring Displacement to Validate Induced Voltage Readings Conclusion: Induced voltage does not reflect displacement. Displacement will be used to make measurements.

Calculation of Young’s Modulus Using Displacement

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

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

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

Testing the Phantom Versaflex Rubber Gelatin Petri Dish

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

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

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

Conclusions Wire cutter did not cut flat surface on wire probes. Assumed area is not correct. Probe does not have good contact with sample. As the probe moves into the sample, full elastic resistance from sample is realized.

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

Conclusions Meeting Criteria Cantilevers are capable of measuring E in the range of skin and fat Accuracy must be improved by making flat probes

Suggestions Use wire saw to cut the probes to ensure flat, even surface Alternative: Use probes as is and… Formulate testing procedure to ensure consistent probe contact area is achieved during testing Determine fitting constant experimentally to determine actual contact area Use fitting constant when calculating E Use E equation for cone geometry

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

Intellectual Property Utility Patent of the three layer design: No current Technologies similar to our device Has a novel, functional, and unique design Driving PZT Sensing PZT Stainless Steel

Regulatory & Environmental Approval by FDA’s Center for Devices and Radiologic Health Effect on the cosmetic and pharmaceutical industry Disposal of device - contains lead

Future Applications Monitoring UV Damage Known to effect skin E and thickness Quantitative effects are currently unclear Progression of a variety skin diseases Psoriasis, Cancer

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

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 `

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

Thom, E. "A Randomized, Double-Blind, Placebo-Controlled Study on the Clinical Efficacy of Oral Treatment with DermaVite on Ageing Symptoms of the Skin." J Int Med Res 33.3 (2005): 267-72. Escoffier, C., de Rigal, J., Rochefort, A., Vasselet, R., Leveque, J. L., & Agache, P. G. (1989). Age-related mechanical properties of human skin: An in vivo study. The Journal of Investigative Dermatology, 93(3), 353-357. Agache, P. G., Monneur, C., Leveque, J. L., & De Rigal, J. (1980). Mechanical properties and young's modulus of human skin in vivo. Archives of Dermatological Research, 269(3), 221-232. Anti-Aging Products. Rep. Jan. & feb. 2009. Global Indistry Analysts, Inc. <http://www.worldhealth.net/news/global_anti-aging_products_market_to_rea>. Merola, Kenneth, Nikiforos Kollias, Jeffrey Pote, and Gregory Payonk. Method of promoting skin care products. Johnson & Johnson Consumer Companies, Inc., assignee. Patent 6922523. July 26, 2005. Hendriks, F.M, Brokken, D., Oomens, C.W.J., Baaijens, F.P.T., and Horsten, J.B.A.M. “Mechanical Properties of Different Layers of Human Skin.” Dept.of Materials Technology, Eindhoben Univ.of Technology, PO Box 513: 5600. References

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