METHODS TO CREATE AND CHARACTERISTICS OF POROUS POLY(VINYL) ALCOHOL FOR THE PURPOSE OF FACIAL IMPLANTS A Thesis Presented to The Academic Faculty by Kathleen Carmen Bernhard In Partial Fulfillment of the Requirements for the Degree Master of Science in the School of Mechanical Engineering Georgia Institute of Technology December 2014 COPYRIGHT © KATHLEEN CARMEN BERNHARD 2014 METHODS TO CREATE AND CHARACTERISTICS OF POROUS POLY(VINYL) ALCOHOL FOR THE PURPOSE OF FACIAL IMPLANTS Approved by: Dr. David N. Ku, Advisor School of Mechanical Engineering Georgia Institute of Technology Dr. Jonathan S. Colton School of Mechanical Engineering Georgia Institute of Technology Dr. Felmont F. Eaves, III Department of Surgery Emory University Date Approved: December 5th, 2014 DEDICATION I dedicate this to my grandfather, Anthony Calandro. A man I never met, but who's lasting legacy helped make this thesis possible. I hope you're proud to know your granddaughter is a Ramblin Wreck from Georgia Tech. ACKNOWLEDGMENTS First and foremost, I would like to thank my adviser Dr. David Ku. His willingness to take me into his lab and give me this research opportunity has meant the world to me. I will always appreciate his constant efforts to strengthen my creativity, critical thinking, and ability to problem solve. His wisdom and mentorship have been invaluable and I will never forget the kindness he has shown towards me. I would like to thank my lab mates, both past and present, who have imparted their knowledge and shown me support: Marmar Mehrabadi, Lauren Casa, Daniel Tanner, Sumit Khetarpal, Max Nguemeni, Susan Hastings, and Joav Birjiniuk. The presence of you all was the most enjoyable aspect throughout this experience. I wish you all nothing but the best in life. I would like to thank my parents, Rudolph and Judith Bernhard, for constantly pushing me to do my best in all aspects of life. They emphasized the importance of education from an early age and instilled in me the work ethic that was required to make it through six years at Georgia Tech and achieve my two degrees. From addition flash cards on my bedroom floor, to weekly vocabulary words on my bed, to physics on the kitchen table, they spent countless hours tutoring and studying with me. When they saw an early interest in math and science, they fostered it with science books, a telescope, and trips to space camp. They taught me to never be ashamed of who I am and to have the belief in myself that I can accomplish my dreams. Everything I am today is because of their unyielding love and support. I would like to thank my younger sister, Kristina Bernhard, whose companionship from childhood through today has been my most treasured gift. I have tried to live by iv your example of fearlessness and self confidence. No matter what happens, I know you will always be there to help me celebrate my victories in life. Finally, I would like to thank my best friend and partner Harrison Jones. His decision of a graduate degree is what prompted me to pursue one as well. He has been by my side through every victory and defeat as well as always there to hold me during a breakdown. Although so much as changed since we met in that freshman dorm, his comforting presence and constant support has been unwavering. His encouraging smile and confidence in my abilities pushed me to achieve all that I have during these six years at Georgia Tech. His love has made a positive everlasting impact on my life and for that I will always be grateful. v TABLE OF CONTENTS ACKNOWLEDGMENTS iv LIST OF TABLES x LIST OF FIGURES xii SUMMARY xiv CHAPTER 1 BACKGROUND 1 Introduction 1 Choosing Volume Filling Facial Implants 3 Nose and Chin Replacements 7 Market Size 7 Regulatory Pathway 7 Current Materials 8 Autografts 10 Homografts 12 Alloplasts 13 Dermal Fillers 19 Market Size 19 Regulatory Pathway 20 Current Materials 21 Characteristics for Facial Implants 25 Elasticity 25 Tensile Strength 26 Elongation 26 vi Tear Strength 27 Pore Characteristics 27 Swelling 28 Summary of Acceptance Criteria for Facial Implants 29 Poly(Vinyl) Alcohol Cryogel 30 Current Methods for Manufacturing Porosity in Polymers 32 Solvent Casting/Particulate Leaching 32 Gas Foaming 33 Composites 34 Summary 36 CHAPTER 2 MATERIALS AND METHODS 37 Experimental Design 37 General Method of Manufacturing Poly(Vinyl) Alcohol 38 Manufacturing the Molds 40 Chin and Nose 40 Extruded Cylinders 44 Molds for Mechanical Testing Samples 45 Overview of Tests 47 Tensile Strength, Elongation Percentage, and Elasticity 47 Tear Strength 49 Pore Characteristics 50 Swelling Ratio 53 Manufacturing Porous Poly(Vinyl) Alcohol Cryogel 55 vii Solvent Casting/Particulate Leaching 55 Gas Forming Method 57 PVA Cryogel Composites 59 Molded Surface 60 Removing Material 62 CHAPTER 3 RESULTS 64 Images of Porous PVA Cryogel Samples 64 Tensile Strength, Elongation, and Elasticity 67 Elastic Modulus 71 Maximum Tensile Strength 73 Yield Elongation Percentage 75 Tear Strength 84 Pore Size 91 Pressed Method 92 Molded Method 92 Casting/Particulate Leaching Method 93 Gas Method 95 PVA cryogel/CS Composite Method 95 PVA cryogel/CaPO4 Composite Method 96 In Relation to Facial implant Criteria 98 Porosity Percentage 101 In Relation to Facial Implant Criteria 101 Swelling 103 viii Summary 106 CHAPTER 4 DISCUSSION 107 Mechanical Properties 107 Elasticity 108 Tensile Strength 109 Elongation 109 Tear Strength 110 Summary of Mechanical Characteristics 111 Pore Structure Characteristics 112 Pore Size 112 Porosity 113 Surface Texture 114 Summary of Porous Characteristics 115 Comparing Porosity to Mechanical Properties 117 Rule of Mixtures 119 Swelling 122 Summary 123 Limitations 125 Potential Future Work 128 Conclusions 129 REFERENCES 130 ix LIST OF TABLES Table 1: List of FDA's Volume Filling Implant Categories ............................................... 5 Table 2: Advantages/Disadvantages of Autografts, Homografts, and Allografts .............. 8 Table 3: Pros and Cons for Current Cartilage Replacing Materials ................................... 9 Table 4: Acceptable Values for Facial Implant Characteristics........................................ 29 Table 5: Converting Young's Modulus to Shore A Hardness ........................................... 73 Table 6: Calculated Tensile Strength, Elongation, and Young's Modulus ....................... 78 Table 7: Tensile Strength and Elastic Modulus Statistical Significance Comparison ...... 83 Table 8: Calculated Tear Strength .................................................................................... 86 Table 9: Tear Strength Statistical Significance Comparison ............................................ 90 Table 10: Pore Size Range and Interconnectivity of Manufactured Porous PVA cryogel 99 Table 11: Porosity Ratio of Manufactured Porous PVA cryogel ................................... 102 Table 12: Swelling Percents (Increase in Volume) of Plain PVA cryogel ..................... 104 Table 13: Summary of Properties of Tested PVA cryogel Materials ............................. 106 Table 14: Mechanical Properties of Popular Biomaterials ............................................. 108 Table 15: Theoretical Values Using Rule of Mixtures ................................................... 121 Table 16: Visual Representation of Equivalence of Value to Required Characteristic .. 124 x LIST OF FIGURES Figure 1: Extruding Silicone Implant ............................................................................... 15 Figure 2: Patient Age Range for Dermal Fillers ............................................................... 20 Figure 3: Intradermal Nodes Formed from Injected PMMA Microspheres ..................... 24 Figure 4: Images and Dimensions of Silicone Facial Implants ........................................ 40 Figure 5: Design of the Nasal Implant .............................................................................. 41 Figure 6: Design of the Chin Implant ............................................................................... 42 Figure 7: 3D Printed Molds for Chin and Nasal Implant.................................................. 43 Figure 8: Aluminum Molds of for Chin and Nasal Implant ............................................. 43 Figure 9: Mold Setup for Extruded Cylinders .................................................................. 44 Figure 10: Image of Extruded Cylinders .......................................................................... 45 Figure 11: Mechanical Testing Shapes ............................................................................. 46 Figure 12: Acrylic Molds Used to Create Samples for Tensile Tests ............................... 46 Figure 13: Tensile Test Over Time ................................................................................... 48 Figure 14: Example of Measuring Pore Size .................................................................... 51 Figure 15: Salt Crystals ..................................................................................................... 55 Figure 16: Image of Proposed Light Bulb Shape.............................................................. 61 Figure 17: Velcro Used to Mold Pores in PVA cryogel ................................................... 62 Figure 18: Method to Create Poked Holes in PVA........................................................... 63 Figure 19: Plain PVA cryogel ........................................................................................... 64 Figure 20: 30% wt PVA Poked with Needle ...................................................................