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Innovative Strategies in Medical Device Development and Entrepreneurship

Explore medical device applications, finite element analysis, prototype development, testing essentials, and creative strategies in device development. Learn about Nitinol stent FEA, value of execution, consulting implications, and valuable resources for startups. Enhance your understanding of simulation vs. testing, sensitivity analysis, model validation, and fatigue testing methods. Discover practical techniques for efficient medical device development and industry insights.

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Innovative Strategies in Medical Device Development and Entrepreneurship

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  1. Medical Device Development and Entrepreneurship Presented by: T. Kim Parnell, Ph.D., P.E.The PEC Group www.parnell-eng.com

  2. Introduction • Overview • Medical Device Development • Device Startups • Consulting 2

  3. Medical Device Applications 3

  4. Some Device Fields… • Cardiovascular • Orthopaedic • Sleep disturbances • Vascular closure • Cosmetic • Etc. 4

  5. AAA DevicesAbdominal Aortic Aneurysm 5

  6. AAA Device 6

  7. Coronary Artery Disease • Stents are used as scaffolds to hold open the artery 7

  8. Finite Element Analysis (FEA) • Design • Life prediction • FDA requirements • Can shorten the design cycle 8

  9. FEA & Testing • Finite element analysis (FEA) and physical testing are complementary • A comprehensive program needs to include both components • With judicious experimental validation, FEA can be used to reduce the amount of physical testing that is needed and shorten the design cycle 9

  10. The Challenge for Medical Device Development • Reduce development time • Increase confidence of success • Avoid surprises and delays 10

  11. Prototype Development • Physical prototype • Cost and lead time is often a limitation • Essential for animal testing and determining needed characteristics • Want to reduce the number of design iterations that are prototyped • Virtual prototype • Assess more design options • Compare alternatives 11

  12. Testing Is Essential for: • Detailed characterization of the material; Getting data needed for the analysis • Fatigue testing taking into account surface finish, processing steps • Validation 12

  13. Nitinol Stent FEA 13

  14. Stent FEA 14

  15. Stent FEA • Rolldown Expansion 15

  16. Stent FEA • Rolldown Expansion 16

  17. Creative Strategies in Medical Devices510(K) vs PMA? • 510(K) • Concept of equivalence • May 28,1976 Medical Devices Amendments to the FDA • Pro’s • Speed • Lower risk • Con’s • Low barriers to entry • 510(K) with clinical trials • PMA – Pre Market Approval • Clinical trials for safety and efficacy of device • Pro’s – barriers to entry • Con’s – time, expense and risk 17

  18. Medical Device Development • Needs Assessment • Research • Intellectual property • Biomedical ethics • Brainstorming • Assessing Clinical and Market Potential • Developing patent strategies • Prototyping 18

  19. Value of Execution • Ref: Rich Ferrari 19

  20. Consulting Implications • Reduced fees for equity? • Incentive • Upside potential • Need some assessment of the company • Capitalization • Burn rate 20

  21. Resources Startups & Business • SVEBP www.siliconvalleypace.com • Stanford BUS16 continuingstudies.stanford.edu • TVC www.techventures.org • TEN www.tensv.org • Girvan Institute www.girvan.org 21

  22. Resources (cont) Medical Device • Stanford Biodesign innovation.stanford.edu • BioDesign Network mdn.stanford.edu • NanoBioConvergence www.nanobioconvergence.org • DeviceLink www.devicelink.com/mddi • TCT www.tctmd.com • Vulnerable Plaque www.vp.org • Vascular News www.CXvascular.com 22

  23. Summary • Many opportunities in medical devices • Entrepreneurs • Consultants • Increasingly multi-disciplinary • Technology can be applied to advantage 23

  24. Carotid Stent 24

  25. Outline of Presentation • Introduction • Simulation vs. Testing • What are the issues? • Benefits of Synergizing Simulation and Testing • Illustrations & Case Studies • Conclusions • Questions?? 25

  26. Sensitivity by Analysis • Material • Tolerance • Variability of the body/target environment • Atypical applications 26

  27. Validation of Model by Test • Analysis of tensile test to confirm ability to predict material behavior • Validation tests for stents might include: • Flat plate loading • Radial expansion • Radial compression 27

  28. Example:Flat Plate Loading Using Contact Note: This “pinching” loading mode is distinct from “radial” loading 28

  29. Are the Assumptions Satisfied? • Make adjustments/corrections as needed so that the model is predictive of the test 29

  30. Additional Information and Insight From Analysis • Get information not available from device testing alone • Internal conditions: stress levels, degree of plasticity, residual stress, transformation fraction 30

  31. Balloon Expandable Stent • Basic steps: • Roll-down for catheter insertion • Inflation and Deployment • Cyclic pulsation loading • Fatigue testing of full device to FDA required 400M cycles is a long process 31

  32. Fatigue and Life Testing • Long test times for full device • Reduce testing of multiple design iterations • Get insight more quickly • Need both analysis and testing 32

  33. Sub-specimen Stent Segment Cyclic Testing of Sub-specimen • Before fatigue testing full device, get more information in less time with sub-specimen • Higher loading frequency, reduced test time • Cycle to failure for a range of loads • Develop part-specific S/N data • Extend with analysis, develop and interpret test conditions in terms of stress & strain • Make predictions for full device 33

  34. Stent Segment and Sub-specimen Sub-specimen Stent Segment Parnell, (2000) 34

  35. Material Testing: Elastic/Plastic • Need more detail than basic data from manufacturer (for example, Min. Yield, Ultimate, Elongation) • Elongation is sensitive to the gage length tested • Reduction of area very useful, particularly for highly ductile materials • Need full stress/strain curve with additional data like reduction of area 35

  36. True Stress E’ Ultimate stress D Eng. Stress Yield stress C E B Proportional limit A Linear Strain hardening Significant necking Plastic 0  Tensile Response of Elastic/Plastic Material Anderson (2002), Biomaterials Typical stress/strain curve for steels. Strains become localized when necking occurs. Standard elongation highly dependent on gage length. Measured area reduction gives correct local strain. 36

  37. Shape Memory Material (SMA) Applications • Unique characteristics • Large recoverable strain range • Super elastic vs. Shape Memory (thermally activated) • Self-expanding devices • Conditions after partial unloading • Load predictions 37

  38. Communi- cation Shape Memory Sports Medical Accessories clothing Home Appliance Industrial Applications Applications for Shape Memory Alloys • Materials that return to some shape upon appropriate temperature change • Applications: 38

  39. Shape Memory Material Properties • DSC to determine transformation temperatures • Tensile test • Behavior as function of temperature • Super elastic material behavior • General features (T > Af ) • Stress-induced martensite and reverse • Shape memory (reverting to learned shape) 39

  40. As [K] Af [K] Ms [K] Mf [K] 188 221 190 128 Transformation Temperatures Miyazaki, et.al., (1981) NiTi Response to Temperature T< Ms Shape Memory(residual strain recovered by heating) Ms <T< AfShape Memory(residual strain recovered by heating) Af <T<Tc Superelastic (SIM)(full strain recovery) T>TcPlasticity before SIM(permanent residual strain) 40

  41. Variation of SMA Structures 41

  42. Pseudo-elastic behavior of SMA • Temperature induced phase transformation • Pseudo-elastic Stress-Strain Behavior 42

  43. Material Testing: Shape Memory Alloy • Transformation temperatures (DSC or other) • Stress/strain tensile curve with unloading • Application may require tensile data at additional temperatures 43

  44. Temperature Dependent Material Behavior of Shape Memory Alloys Nickel-Titanium alloys show temperature dependent material behavior. Shape memory effect (that deformed specimens, regained their original shape after a loading cycle) is observed at a certain temperature. NiTi Stent 44

  45. Cs Cm To Input: Cm Cs To Input data for Mechanical SMA 45

  46. Differential Scanning Calorimetry (DSC) • DSC can be used to determine transformation temperatures of shape memory materials • Heating curve:As,Af • Cooling curve:Ms,Mf • Austenite is Cubic (BCC) • Martensite is Monoclinic 46 Shaw & Kyriakides, (1995), (courtesy of M.-H. Wu )

  47. Shape Memory Effect (SME) Shape memory effect is a consequence of a crystallographically reversible solid-solid phase transformation occurring in particular metal alloys (Ni – Ti, Cu based alloys). This transition occurs between a crystallographically more-ordered phase (called austenite) and a crystallographically less-ordered phase (martensite). 47

  48. Stability for Martensite and Austenite Phases 48

  49. Vulnerable Plaque • Morphology • Tissue characteristics • Tissue properties and geometry become important in evaluating device Christensen, (2002) 49

  50. Inverse Analysis Problem • Correlate material properties to measured behavior • Use to estimate ranges of properties for tissue • Example: estimation of vessel wall cyclic strains from cine PC-MRI data (Draney, et.al., 2002) 50

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