Novel Skin Stretching Device A Major Qualifying Project Report submitted to the Faculty of Worcester Polytechnic Institute in partial fulfillment of the requirements for the Degree of Bachelor of Science by ___________________________ Katie Hutchinson __________________________ Daniel Keenan ___________________________ Laura Piccione ___________________________ Hussein Yatim May 2012 Approved by: ___________________________ Professor George Pins, Advisor ___________________________ Professor John Sullivan, Advisor Amanda Clement Dr. Michael Chin Dr. Raymond Dunn Dr. Ronald Ignotz Dr. Janice Lalikos Keywords: skin graft, in vitro, cyclical testing Table of Contents Table of Contents ................................................................................................................ 1 Authorship Page .................................................................................................................. 5 Acknowledgements ............................................................................................................. 6 Abstract ............................................................................................................................... 7 Table of Figures ................................................................................................................... 8 Chapter 1: Introduction .................................................................................................... 10 Chapter 2: Literature Review ............................................................................................ 13 2.1 Clinical Significance ............................................................................................. 13 2.1 A The Importance of Skin .................................................................................. 13 2.1 B The Need for Skin Substitutes ....................................................................... 14 2.2 Current Skin Grafts .............................................................................................. 15 2.2 A Biological Tissues ........................................................................................... 16 2.2 B Engineered Tissues ........................................................................................ 17 2.2 C Limitations ..................................................................................................... 19 2.3 Improving the Current Gold Standard ................................................................ 20 2.3 A The influence of Mechanical Stress ............................................................... 20 2.3 B The Limitations of Current Technology ......................................................... 21 2.3 C Moving From an in vivo to an in vitro Model................................................. 22 2.3 D Proposed Contribution to the Field ............................................................... 22 2.4 Relevant Mathematical Models .......................................................................... 23 Chapter 3: Project Strategy ............................................................................................... 27 3.1 Initial Client Statement ....................................................................................... 27 3.2 Objectives ............................................................................................................ 28 1 3.3 Constraints .......................................................................................................... 30 3.4 Revised Client Statement .................................................................................... 32 3.5 Project Approach ................................................................................................. 33 Chapter 4: The Design Process ......................................................................................... 35 4.1 Introduction......................................................................................................... 35 4.2 Needs Analysis ..................................................................................................... 36 4.3 Functions and Specifications ............................................................................... 38 4.4 Preliminary Designs ............................................................................................. 42 4.4 A The Column Design ........................................................................................ 44 4.4 B The Custom Fit Design ................................................................................... 45 4.4 C The Expanding Ring Design ............................................................................ 46 4.4 D The Piston Design .......................................................................................... 47 4.4 E Summary ........................................................................................................ 48 4.5 Final Design ......................................................................................................... 49 4.5 A Design Refinement ........................................................................................ 50 4.5 B The Device ...................................................................................................... 51 4.5 C Dimensional Analysis ..................................................................................... 54 4.5 D CAD Drawings ................................................................................................ 57 4.5 E Machining ....................................................................................................... 58 Chapter 5: Design Verification .......................................................................................... 59 5.1 Preliminary Data .................................................................................................. 59 5.1 A Pullout Testing ............................................................................................... 59 5.1 B Force Calculations .......................................................................................... 59 5.1 C Power Output Required for Motor ................................................................ 60 2 5.1 D Rack and Pinion, Motor, and Load Cell ......................................................... 60 5.2 Design Feasibility ................................................................................................. 62 Chapter 6: Discussion ........................................................................................................ 65 6.1 Product Impact .................................................................................................... 66 6.2 Environmental Impact ......................................................................................... 66 6.3 Economics............................................................................................................ 67 6.4 Societal Influence ................................................................................................ 67 6.5 Political Ramifications ......................................................................................... 68 6.6 Ethical Concerns .................................................................................................. 68 6.7 Health and Safety Issue ....................................................................................... 68 6.8 Manufacturability ................................................................................................ 69 6.9 Sustainability ....................................................................................................... 70 Chapter 7: Validation ........................................................................................................ 71 7.1 Sterility and Gas Exchange .................................................................................. 71 7.1 A Procedure ...................................................................................................... 72 7.1 B Results ............................................................................................................ 73 Chapter 8: Conclusions and Recommendations ............................................................... 75 8.1 Conclusions.......................................................................................................... 75 8.2 Recommended Analytical Data ........................................................................... 75 8.3 Characterization of Cells in Scaffold .................................................................... 76 8.4 Future Modifications ........................................................................................... 76 References ........................................................................................................................ 78 Appendices ........................................................................................................................ 84 Appendix A: The Design Process ................................................................................... 84 3 Appendix A.1 Gantt chart ....................................................................................... 84 Appendix A.2 Pairwise Comparison Chart .............................................................. 85 Appendix A.3 Metrics .............................................................................................. 89 Appendix A.4 Evaluation