Sand and Swim Leg, is addressing the clinical need of limited options for lower-limb amputees to participate in water activities. We will follow the FDA Medical Device Design Process throughout our two semester course. Initially, we created our team agreement and delegated team roles and responsibilities. Then, we conducted background research on the clinical need, competitive products, and existing patents. After compiling and discussing research amongst our team, we contacted stakeholders that would be affected by our product. Our stakeholders include our below-the-knee amputee client, an above-the-knee amputee, pediatric prosthetists, and our client’s prosthetists. We conducted interviews with our stakeholders to gain perspective on issues, successes, experiences with current prosthetics. Some issues that are present for current solutions include, uncomfortable, lack of ability to enter and exit the water, and expensive. We will follow up the User Needs stage of the process with the Design Input, Design Process, and Design Output. Our end goal for this process is a way for below-the-knee amputees to participate in water activities that is more affordable, functional, and comfortable than current options

Davidson, Chloe

Galford, Jessica

Lindsay, Reagan

McLaughlin, Victoria

Testa, Allison

English

The University of Akron

The University of Akron IdeaExchange@UAkron Williams Honors College, Honors Research Projects The Dr. Gary B. and Pamela S. Williams Honors College Spring 2022 Sand & Swim Leg Victoria McLaughlin vrm16@uakron.edu Allison Testa The University of Akron, akt32@uakron.edu Chloe Davidson The University of Akron, cad150@uakron.edu Reagan Lindsay The University of Akron, rml74@uakron.edu Jessica Galford The University of Akron, jg174@uakron.edu Follow this and additional works at: https://ideaexchange.uakron.edu/honors_research_projects  Part of the Orthotics and Prosthetics Commons Please take a moment to share how this work helps you through this survey. Your feedback will be important as we plan further development of our repository. Recommended Citation McLaughlin, Victoria; Testa, Allison; Davidson, Chloe; Lindsay, Reagan; and Galford, Jessica, "Sand & Swim Leg" (2022). Williams Honors College, Honors Research Projects. 1506. https://ideaexchange.uakron.edu/honors_research_projects/1506 This Dissertation/Thesis is brought to you for free and open access by The Dr. Gary B. and Pamela S. Williams Honors College at IdeaExchange@UAkron, the institutional repository of The University of Akron in Akron, Ohio, USA. It has been accepted for inclusion in Williams Honors College, Honors Research Projects by an authorized administrator of IdeaExchange@UAkron. For more information, please contact mjon@uakron.edu, uapress@uakron.edu. May 2022             1 Sand and Swim Prosthetic  Chloe Davidson Department of Biomedical Engineering The University of Akron Akron, Ohio cad150@uakron.edu  Victoria McLaughlin Department of Biomedical Engineering The University of Akron Akron, Ohio vrm16@uakron.edu   Jessica Galford Department of Biomedical Engineering The University of Akron Akron, Ohio jg174@uakron.edu      Reagan Lindsay Department of Biomedical Engineering The University of Akron Akron, Ohio rml74@uakron.edu  Allison Testa Department of Biomedical Engineering The University of Akron Akron, Ohio akt32@uakron.edu I. Introduction There are currently limited options that allow below-the-knee (BTK) amputees to transition from land to water effectively and allows for easier participation in water activities. We have designed the Sand and Swim Leg to be an affordable alternative to other swim legs and devices on the market. Our design is a waterproof and sand proof weight-bearing attachment to the socket of a BTK amputee. Most swim legs currently on the market are thousands of dollars and have a limited functionality. Because of this, BTK amputees only have the option of buying an expensive swim prosthesis or deciding to swim with only their residual limb, which can make swimming a more difficult task. By creating the Sand and Swim Leg, we provide a more accessible and useful option for BTK amputees who wish to participate in water activities. II. User Needs To create a working idea of how the Sand and Swim Leg would address the issues discussed above, a list of user needs was developed from interviews with stakeholders, discussions with prosthetists, and background research. The main priorities found in the user needs stage were functionality, durability, comfort, and safety. The needs of the user encompassed the goal of this project, which was to create a functional weight-bearing swim leg for BTK amputees. Careful consideration went into all the properties deemed necessary for the end product to be considered successful. The compilation of all user needs may be found in Appendix B. III. Design Inputs To ensure the Sand and Swim Leg met all user needs, the needs were translated into engineering requirements. The engineering requirements gave specific and measurable values to achieve regarding the device design. These requirements focused on creating a device with performance characteristics, safety, and cost and resources in mind. The full list of engineering requirements can be found in Appendix B. A quality function deployment (QFD) matrix was created to assess how the user needs correlated to the engineering requirements, as shown in Appendix C. The QFD also shows how the engineering requirements relate to each other, how competitive products compare to the Sand and Swim Leg, and target values for the device design to meet. A preliminary risk assessment was performed on the conceptual device design using a failure mode and effects analysis (FMEA), as shown in Appendix F. The FMEA was updated through the remainder of the project to mitigate as many risks as possible.  To mitigate risks during the testing phase, we included the following standards as design inputs for consideration: ASTM D695 – Standard Test May 2022             2 Methods for Compressive Properties of Rigid Plastics, ASTM D638 – Standard Test Methods for Tensile Properties of Rigid Plastics, and ASTM D790 – Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials. IV. Design Process To produce an initial design, a concept map was created to decide which components would be part of the final design. From there, sketches of ideas were created, until we had refined which specific components we would include. When designing the device, we created a decision matrix to decide on which materials to make each component from. The results of the down selection can be found in Appendix D. A part design matrix, seen in Appendix E, was also created to ensure the user needs and engineering requirements would be met by our device. The Sand and Swim Leg was designed to be undamaged by UV rays, salt water, fresh water, and sand and weigh less than 8 pounds total. The device was also designed to not fracture under intended use and have proper traction on the foot to ensure the user’s safety. V. Design Outputs After completing the design process, we needed to make sure the prototype met all engineering requirements, and that all risks were mitigated. As seen in Appendix C, a parts design matrix was used to determine how to ensure each component of our project would meet the engineering requirements listed in Appendix B. The combined pylon and pyramid piece was constructed using Rigid 10K resin and was 3D printed. The foot component was composed of a Nomex honeycomb and aluminum plate core, surrounded by carbon fiber sheets and epoxy. The fin was constructed using Shore 80A resin and 3D printed. The device was assembled using 316L stainless steel screws. All materials used can be found in the bill of materials, as seen in Appendix H. Shown below in Figure 1 is the SolidWorks assembly of the pylon/pyramid, the fin, and the foot components of our project.   Figure 1: SolidWorks Assembly of Sand and Swim Leg VI. Design Verification Materials testing is an imperative part of the design process. To ensure the materials used in the design of the Sand and Swim Leg met the device specifications, Instron testing machines were used for tensile, compression, three-point bending, and friction tests. In the first round of prototyping, we were planning on using Grey Pro, a material with lower tensile and compressive strength as compared to Rigid 10K resin. The testing showed that the material passed the engineering requirements, however, was not as strong as we would have liked. The stress-strain curves for the Grey Pro are shown below in order of compression, tension, and three-point bending (Figures 3-5). May 2022             3  Figure 2: Compression Stress-Strain Curve for Grey Pro  Figure 3: Tensile Stress-Strain Curve for Grey Pro  Figure 4: Three-Point Bending Stress-Strain Curve for Grey Pro The tests shown above, along with the friction test for the material used on the bottom of the carbon fiber foot, a water displacement test, and a wind tunnel drag test, all showed that the materials used passed our engineering requirements. Because Rigid 10K resin is stronger than Grey Pro, this shows that the Rigid 10K resin is an adequate material to use for building the pyramid/pylon component.  VII. Medical Device The final prototype, as shown below in Figure 5, is a weight-bearing waterproof attachment to a pre-existing BTK socket. The bottom of the pylon/pyramid screws into the carbon fiber foot using 316L stainless steel screws. The top of the pylon/pyramid component is where a BTK amputee would screw the device onto their own socket. The flexible resin fin clips onto the pylon/pyramid component as shown.  Figure 5: Carbon Fiber Foot, Pylon/Pyramid, and Fin After verification and validation, the prototype was found to meet device specifications.  VIII. Validation Testing For validation, we created methods for each customer requirement. The customer requirements can be seen in Appendix B, and to validate these, we used a combination of inspection, visual confirmation testing, and a questionnaire. The questionnaire is intended for stakeholders of the device and will be given to BTK amputees as well as prosthetists to confirm the Sand and Swim Leg meets or exceeds expectations. Inspection was used for evaluating natural swimming wearing the device and May 2022             4 being easy to clean off. All validation tests performed have passed. IX. Risk Mitigation Process One of the key elements in the design process is risk assessment. Risk assessment provides a way to ensure no unacceptable risks are overlooked. For the Sand and Swim Leg, the main risk factors would be if the device were to break while in use. Some risks are more severe than others. If the pylon/pyramid breaks, the user will lose balance and fall. A less severe risk is the fin detaching from the pylon/pyramid. Both are considered risks that must be mitigated; however, one failure would be much more catastrophic than the other. To analyze all risks in this way, a design failure mode and effects analysis (dFMEA) was created. The Risk Summary Table outlines each risk and can be found in Appendix F. Overall, the benefits of this device outweigh the residual risk. After the risks were mitigated, each received a ranking of low risk, and the device would greatly improve quality of life for BTK amputees who wish to participate in water activities. X. Marketing and Manufacturing Considerations The current market for swim legs for BTK amputees is very limited, and what little is out there is very expensive. Our project is a much cheaper alternative, and also stands out by being a weight-bearing leg. The Sand and Swim Leg cost under $1000 to make, whereas competitors’ prostheses cost anywhere from $3000-$5000. The $1000 to build the Sand and Swim Leg also includes the resin tanks for the Shore 80A and the Rigid 10K, which would only be a one-time expense. Creating more devices in the future would cost $600 or less, making the production cost for every device after the first would be around $400 per device. Doubling this to account for labor costs, doubling again to account for company overhead, and adding a 60% margin for sale price, this comes out to $2560, which is still hundreds of dollars cheaper than current competitive products. XI. Summary Feasibility Discussion The Sand and Swim Leg did satisfy the user needs once completed. The device is strong enough to be weight-bearing, has a good traction, is waterproof, and improves swimming capabilities. While the created device does meet the user requirements, it is still considered a prototype, as the product is made to be highly personalized from customer to customer. Without having a person’s specific measurements for their residual limb, the height of the device and the size of the foot is an approximation. The resulting prototype, however, is still fully functional. XII. Discussion, Lessons Learned, and Conclusions Overall, the Sand and Swim Leg turned out to be very successful. We had help from many different sources for testing, designing, and creating the prototype. There were several setbacks along the way, but this only improved the final product. Up until the end of the Design Output stage, we had planned to use a 3D printed material called Grey Pro. We had no capabilities to test in shear or torsion, but the tensile, flexure, and compression testing done on the material met the engineering requirements. After learning that Grey Pro is not nearly as strong in shear or torsion, however, the pylon/pyramid printing material was changed to Rigid 10K resin. This resin is stronger than the Grey Pro and exceeds our needs. Also, when printing the pylon/pyramid component, the orientation of the print made the part print and cure incorrectly. We adjusted the design to fit the capabilities of the printer, and the second print was successful. To stay on top of the workload, weekly team meetings were set, and monthly meetings were held with Dr. Nguyen, our project mentor. Dr. Nguyen was a major help in pushing past difficulties and helped the design process run smoothly. XIII. Future Work Looking toward the future, the Sand and Swim Leg design could be used to create customized swim legs May 2022             5 for BTK amputees. There are still improvements that could be made and more testing to be done, but the prototype has proven to be a viable option for a swim leg. To reduce risk further, the model could be adjusted to fit the induvial user’s needs.  XIV. Individual Roles and Responsibilities Throughout the past two semesters, each member of the group has put in a significant amount of effort and time into this project. Allison Testa has made major contributions in connections to prosthetists, created the pylon/pyramid structure in SolidWorks, and has aided in the completion of all documentation. Allison has also done background research for competitive projects, helped with material testing, and has helped in all reports and gate review presentations. Chloe Davidson has focused on report writing, material testing, and has also helped with documentation along the way. Chloe wrote most of the honors final report and has also aided in data analysis and gate reviews. Jessica Galford has led the group in material data analysis, helped with report writing, and has also contributed to the documentation of the process. Jessica has kept the files organized, has helped with gate review presentations, and has also been a key component in communications with our mentor and professors. Reagan Lindsay has done all meeting documentation, is the main communicator to stakeholders, and has helped with design process documentation. Reagan has also done simulations on our SolidWorks parts, created most of the validation methods, and has helped with gate review presentations. Victoria McLaughlin has delegated most tasks, helped with documentation and testing, and designed the fin and foot parts of our project. Victoria also aided in process documentation and gate reviews and has been the lead in the carbon fiber layup process for the foot. Overall, each team member has contributed a significant amount of time and effort to this project. XV. Professional and Ethical Responsibilities The Sand and Swim leg has considered the impact it will have in many different areas of consideration. This design provides a way for BTK amputees to swim with a weight bearing leg without worrying about ruining their everyday use leg. The Sand and Swim leg is also more cost effective and makes swimming more accessible for many BTK amputees. XVI. Acknowledgements We would like to acknowledge and thank our design professor, Dr. Keszenheimer as well as our mentor, Dr. Nguyen for their continued support and help. We would also like to thank Steve Patterson, Dr. Noble, Dr. Garafolo, Eric Pfiffner, Pamela Schram, George “Bud” Weisgarber, Gene Yeager, Alex Betancourt, Abbey Calderone, and all who have helped along the way. References 1. Nakashima, Motomu & Suzuki, Shingo & Ono, Ayako & Nakamura, Takashi. (2013). Development of the Transfemoral Prosthesis for Swimming Focused on Ankle Joint Motion. Journal of Biomechanical Science and Engineering. 8. 79-93. 10.1299/jbse.8.79. 2. Nathalie Alexander, Hermann Schwameder, Lower limb joint forces during walking on the level and slopes at different inclinations, Gait & Posture, Volume 45, 2016, Pages 137-142, ISSN 0966-6362, https://doi.org/10.1016/j.gaitpost.2016.01.022.  3. Northwell Health. (2011). https://www.northwell.edu/research-and-innovation/the-fin 4. Protosthetics. (2017). https://protosthetics.com/amphibian/ 5. Krassenstein, Brian. (2014). Elle: The Incredible 3D Printed Swimming Leg for Amputees. https://3dprint.com/22221/elle-swimming-prosthetic/ 6. AmpFins. (2021). https://ampfins.com/  Appendix May 2022             6 Appendix A Gantt Chart:   Appendix B User Needs: May 2022             7 1. Materials are not damaged by use in water or on sand Device should enhance straight-line swimming  2. Materials shall be corrosion resistant  3. Prosthesis shall not rotate, or detach while in use  4. Device shall be able to hold up person's body weight while walking on various terrain  5. The device should not sink when used in the water  6. A non-skid tread shall be present on the bottom of the foot   7. Water resistance should be adjustable for the user   8. Price shall be comparable to current market costs  9. User should be able to maintain stability when traversing uneven/unstable terrain such as sand or boats             10. Device should be clean after rinsing with water  Engineering Requirements: 1.0 User/Patient/Clinical Performance Characteristics  1.1 Improved Straight-Line Swimming Ability  1.1.1. The device shall enhance the function of the amputated leg while  swimming  1.1.2. The device should float  1.1.3. The fin shall have low drag in fluid  1.1.4. The device shall have no water time limitation  2.0 Safety  2.1. Mechanical  2.1.1. The device shall withstand average male weight with a safety factor  2.1.2. The device shall have a non-slip rubberized material on the bottom surface  2.1.3. The device shall have no easily corroded metal components  2.1.4. The device shall weigh between three and ten pounds  2.1.5. The device shall be able to be disinfected    3.0 Cost & Resources  3.1. Affordability  3.1.1. The total cost of the device shall be less than or equal to $3,000   Target Values:  May 2022             8   Appendix C QFD:  Full QFD (Customer Requirements, Engineering Requirements, Target Values, Competitive Product Analysis, and Correlations) May 2022             9 Competitive Product Analysis: Where 1 = Worst, 5 = Best  May 2022             10 Appendix D Decision Matrix: Pylon PVC 3D Printed Single 3D Printed w/ Pyramid 11 9 12 Foot Prosthetic Foot Carbon Fiber Blade 3D Printed Model 5 12 10 Fin Polymer, Clipped Polymer, Velcro Rigid, Slot 13 11 8 Feasibility Rankings for Each Component Appendix E Part Design Matrix: Relationships Key  Pyramid  May 2022             11 Pylon  Foot    May 2022             12 Fin                 May 2022             13 Appendix F Risk Summary Table:  May 2022             14   May 2022             15 Appendix G Validation Matrix:             May 2022             16 Appendix H Bill of Materials:   

Sand & Swim Leg

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Sand & Swim Leg

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