Embedded Files
For my biomedical capstone project, I decided to assist a fellow teammate of mine, Drennan. He is currently a Freshman at Providence Day and was the youngest athlete to win gold (at only 11!) in the 2021 U.S. Paralympics Swimming National Championships. Drennan is a para-athlete. His diagnosis is a congenital left foot drop with left lower extremity atrophy. This is a condition present at birth where the left foot has difficulty lifting (foot drop) and there's muscle wasting (atrophy) in the lower leg. During practice, a training tool our team uses is fins. Unfortunately, Drennan either has to wear one fin on his dominant foot and a smaller size on the other, or no fin at all. I attempted to create a silicone sock-like prosthetic. This sock would go over his smaller foot, adding up to fill this interior of a the larger size fin he wears on his dominant foot. Here is a link to the fins he wears. He wears the TYR Crossblades, with his left leg in the XXS size (Orange fin below and Shoe Size 1-3), and his right leg in the S size (Yellow fin below and Shoe Size 5-7). This way he will be able to wear the same size fin on both feet, allowing him the same advantage that his peers without disabilities are given while practicing with fins.
Plan of Approach
Original:
Contact Drennan and his mom to gain approval.
Cast leg with plaster bandage - cast in two parts (top and bottom) because I don't have access to a cast cutter
Scan the model
Size this up to match the dominant foot
3D print this sized-up model
Place original model in the sized-up, printed-out model
Fill space in-between with silicone
Final:
Contact Drennan and his mom to gain approval.
Cast leg with plaster bandage - was able to go all the way around and cut off with scissors
Make a 3D model with the scanning apps of the cast
3D print this model
Place the model inside of the larger size fin, pour silicon around it, into the fin
Idea Generation
https://design.osu.edu/research-gallery/propel-swimming-prosthetic
Originally, I planned to make a silicone part that had a fin physically connected to it with a joint at the ankle, inspired by this undergraduate capstone project by John Greene of Ohio State University. I then realize that Drennan would have to put his foot into it, and already had an ankle.
This site above will lead you to the company, the Amputee Store, that produces silicone socks, this model is the Silipos sock, that goes over an amputated limb. Though Drennan is not an amputee, I have settled on using a similar idea. I will create a silicone sock that will go over his foot, instead of a limb, and it will enlarge his foot to be the size of his other, dominant foot.
Daily Journal
March 7, 2025: Came up with idea for project. Reached out to Drennan and his mom to make sure they were comfortable with helping me with this project.
~ We continued with normal lessons in class and would return to the project later
April7, 2025: I did research on digital 3d modeling. I found this video on how to scan an item with an app called KIRI. I made a test model of my right foot and my right TYR Hydroblade fin.
April 8, 2025: I tried another scan of my left foot with more pictures in a darker place.
April 9, 2025: I downloaded the Polycam app and worked with my right foot.
April 10, 2025: I used the shadow box to collect better photos of my foot.
April 11, 2025: I went to the athletic trainer at my school and had her wrap my foot - experimental.
April 14, 2025: Came up with idea to create cast around my leg to make a model. Contacted my mom, an ER Physician, to ask for casting supplies.
April 15, 2025: Made the first cast. Originally planned to do two layers, so I made the first layer.
April 16, 2025: Made another cast, all the way around my foot - failed.
April 17 - 21, 2025: Easter Break
April 22, 2025: Documentation and exporting a file to Fusion360.
April 23, 2025: Made a full leg cast again of my foot - success.
April 24, 2025: D0cumentation and reached out to Drennan to schedule a time to make a cast of his foot.
April 25, 2025: D0cumentation and research on next steps.
April 28, 2025: Contacted TYR in hopes of obtaining a 3D model or scan of the size S TYR Crossblade fin.
April 29, 2025: Waited for a response, documented.
April 30, 2025: Ordered silicon. Made a cast of Drennan's foot.
May 1, 2025: Hot-glued the seam of Drennan's Cast and fixed some impurities.
May 2, 2025: Made a 3D scan of Drennan's cast.
May 6, 2025: Started a 3D print of Drennan's foot model. It failed.
May 7, 2025: Made a smaller Fusin360 model of Drennan's foot and made a 3D print to make sure the foot would print well.
May 8, 2025: Started a print of Drennan's full-sized 3D model.
May 12, 2025: Sanded the 3D model with a vacuum sander.
May 13, 2025: Documentation.
May 14, 2025: Documentation.
May 19, 2025: Pour silicon
May 20, 2025: Take silicon and foot model out of fin - continue to let the silicon dry.
May 21, 2025: Take silicon off of the model - DUE!
KIRI Scanning App
The app that I used to create the 3D models of the feet is called KIRI. It can be downloaded onto both an Android and iPhone (link to app is embedded). It can create models through LiDAR scanning technology, photo scan, featureless object scan, and 3DGS scan (3D Guassian Splatting - an advanced rendering technique). However, the featureless object scan and the 3DGS scan required the purchase of premium (a whopping $80 a year). The phone that I used to create the model does not have the most recent LiDAR technology and therefore I could not use it. I used the photo scanner. I had to take pictures (a minimum of 20) of the object I was scanning and upload them to the application. It took a while to upload, more pictures took a longer amount of time. After uploading, a 3D object was created that could be exported. It appeared that the free account had a limited number of exp0orts, therefore I took screen recordings of my test models to save the exports for the final 3D models.
ScreenRecording_04-07-2025 11-58-30_1.mp4To the left is a recording of my very first scan. I took 22 pictures of this right fin. I learned from this that the more pictures were taken, the better the image would come out.
ScreenRecording_04-08-2025 14-50-10_1.mp4To the left is a recording of my first scan of my right foot. I took ~40 pictures of my foot in the middle of the classroom. As you can see, the scanner was confused by the objects in the room and did not focus on my foot.
ScreenRecording_04-09-2025 12-15-07_1.mp4To the left is a recording of my second scan of my right foot. I watched the tutorial I had linked above and went into a dark room and used a light to minimize distractions. I took ~70 pictures. It still had a hard time focusing on my foot and captured the room instead.
Polycam Scanner
After these trials, I tried a different phone scanning app. This was to ensure that I was using the best scanning application I could. The only significant difference was Polycam allows me to make a photogammetry mesh or a Guassian Splat model without the purchase of premium. It also allowed to take a 360° video of the object. Another difference is that the yearly subscription for their pro is $199.99. The link to this app on the iPhone.
ScreenRecording_04-09-2025 11-36-25_1.mp4To the left is a recording of my second scan of my right foot. I used the same ~70 pictures that I had used for the second trial on KIRI. Polycam focused on the room itself. A primary use of Polycam is room and interior design.
ScreenRecording_04-10-2025 14-59-22_1.mp4To the left is a recording of another scan of my right foot. This time, we used a shadow box. This allowed me to minimize distractions, have a white background, and better lighting on my foot. As you can see, I got the scan to focus on my foot, finally, yet the bottom of my foot and shin were not captured.
Fusion360 Modeling
From the scanning apps, I was able to send these scans to Fusion360. To practice using this skill, I using the scan of my fin. Though it was not the greatest scan, Fusion360 made a mesh that resembled this scan. Below is a comparison of the scan (left) to the mesh (right). Here is the link to my Fusion360 model of the fin.
VS
Athletic Trainer Wrap
After having difficulties with scanning my foot, I decided I needed a model. It was too hard to get pictures all around my foot, as you can see from the last scan. I could perfectly get pictures of the top, however could not get the bottom of my foot or shin. I first thought of paper mache, however it is messy and I am not sure how stable it is. My friend, a volleyball player, suggested I have my foot wrapped, remembering from her own experience, the wrap, once removed, typically holds its shape. I had them wrap my foot and part of my shin, which the trainer informed me they do not typically do. Therefore, the wrap was not the best model of my foot. It was very thick around my foot and the material did not hold its shape well as it is very bendy. Below are some pictures of the model after being wrapped and removed. The picture farthest to the right shows that I stuffed the wrap with paper towels in an attempt to improve the stability, however it was still not sturdy enough.
Casting Model
After the wrapping model did not come out the way I had hoped, I came up with the idea to create a cast around my leg. My mom is a physician in the ER and was able to get me the supplies: Plaster bandage rolls (x3), a hospital bucket (to wet the bandages), and some plastic gloves. Originally I had planned to create the cast in two pieces. Normally, casts are required to be removed with a cast saw. Therefore, I first made a top layer. I wrapped my foot in plastic cling wrap to protect it from the plaster. After I had started placing the plaster on top of it, the cling wrap, by itself, started to come up. The next time I plastered, I taped around the wrap and especially around my ankle to create the model flush to my leg. After the first cast had sat overnight, I realized I could cut through it quite easily. I then made another cast all the way around my leg. On this cast, I went around my leg only once with the plaster wrap. It ended up being really flimsy and ripped in certain spots. One the next cast, I wrapped each part of my foot twice. My mom gave me a tip to squeeze out the plaster after wetting it, which also helped it solidify faster and made it more solid.
The two pictures above are of my first one-piece cast of my foot.
These three pictures above are of the first full-leg cast of my foot. As you can see, it has multiple holes and is falling in on itself.
These two pictures above are of the second full-leg cast of my foot. It is much sturdier and more flush to my leg.
Contacting TYR
Before I had the opportunity to cast Drennan's leg which we scheduled for Wednesday, April 30, I thought of possible things to do while awaiting the cast and the fin he would bring with him. Without the fin, I couldn't make a 3D scan. I found out that I could contact TYR through their "Contact Us" page (linked here). I wrote them this:
"Hello! I am a bioengineering student from Charlotte, NC. I am currently making a silicone sock-like prosthetic for a paralympic swimmer who is a friend of mine. Right now, he wears a size S of the TYR crossblades fin on his right foot (his dominant foot) and a size XXS on his left foot. I was wondering if it was possible for you to send me a 3D model or scan of the inside of the S size of the TYR crossblades fin. With this, I will be able to mold the silicon sock to this interior of the fin so he is able wear this sock and fit his foot into the larger size. This way he will be able to wear the same size fin on both feet, allowing him the same advantage that his peers without disabilities are given while practicing with fins. Please let me know if this is a possibility! Thank you so much!"
There was a space for additional comments where I wrote:
"This means a lot to my friend and I, so thank you for taking the time to review this. Let me know if you would like to know more about my process and how it is coming so far."
It redirected me to "Production@TYR.com" and I sent the text above to this email. There was no response.
Drennan Cast
After our practices one afternoon, I had Drennan come to the lab so I could make a cast of his foot. It took around 45 minutes and I made sure to use multiple layers on all areas of his foot so that the model would be sturdy and would dry faster. I cut down the side, as pictured in the photographs below, and it came out nicely.
This was taken while the cast was drying.
I taped it immediately after taking off the cast to hold its shape and hot-glued the cuts later. All of the cuts I used to remove the cast are pictured.
3D Scanning Drennan's Cast
I used the KIRI scanning app to scan Drennan's cast. I held the cast with the foot up, getting pictures 360° around the cast. It came out great after the first scan. I didn't need the entire area that it scanned, so I cropped it in the app and then downloaded the edited file: https://drive.google.com/file/d/14AkEAhqwS-AeMtmd6w1y5LGMdqtsFWhD/view?usp=drive_link.
ScreenRecording_05-19-2025 19-49-58_1.mp4ScreenRecording_05-19-2025 19-50-14_1.mp4Above are two videos of the scan of the cast. The one to the left is of the unedited scan, and the one on the right is the edited scan.
Fusion360 Cast Model
I sent the scan's file to Fusion360. This is the file: https://a360.co/3ERbDa3. I then converted the mesh to a solid. Below is what the scan looked like in Fusion360.
3D Printing Drennan's Model
I then saved this Fusion360 file and sent it to Bambu Studio. When the file was first exported into Bambu Studio, the dimensions were way off. The size wasn't anything close to the cast of Drennan's foot. I used calipers to figure out the distance on one spot of the cast to another and then I used the measure tool in Bambu Studio to measure the distance between the same two spots on the model online. I was able to size the model up based off of this calculation by finding the percent I needed to increase the model's size by. I made sure to add tree supports so that the model would print correctly. Before I printed this correctly-sized model, I saved the file, and made a copy. In this copy, I sized the model down significantly and printed that first, to make sure that the real model would print correctly. Once it did, I also printed the regular model. The files are linked below for these two models in Bambu Studio.
https://drive.google.com/file/d/11oHT0erDhJNgzq6T7FX7TEN0bha5WgMD/view?usp=drive_link - the small 3D model
https://drive.google.com/file/d/1j6vWQY6yzcaWWxgqlxgv6x_7Epc__eP3/view?usp=drive_link - the exact 3D model
Above are two pictures of the smaller 3D model in Bambu Studio, the one on the left shows the display in the editing portion of Bambu Studio and the one to the right showing the time that is required to print the model.
Above are two pictures of the correctly-sized 3D model in Bambu Studio, the one on the left shows the display in the editing portion of Bambu Studio and the one to the right showing the time that is required to print the model.
This photograph is of the smaller model after it was printed.
This photograph is a comparison between the cast and the smaller model.
This photograph is of the correctly-sized model compared to the cast.
After being printed, there were some bumps left by where the tree supports were added. I sanded them down with a vacuum sander.
Silicon Casting
The silicon that I used for this project was Smooth On's "Ecoflex 00-33AF Anti Fungal" silicon. It bends very easily and is hard to tear. The blue (Smooth-Sil 940) and the pink (no product description) were other examples that the lab has. The clear example is the "Ecoflex 00-45 Near Clear" model, however the Anti Fungal version of the Ecoflex variety is better when making prosthetics. It is slightly more flexible, which shouldn't be a problem as it will improve comfort. The FabLab at Charlotte Latin offers a course called FabAcademy. Their lesson the week I was pouring the silicon was about molding and casting. Their lesson was recorded here, and I watched to gain some extra tips to remember when making the sock.
IMG_2218.MOVIn this video, you can see the durability and stretch of each type of silicon. The clear was the stretchiest, the blue was much less bendable, and the pink was slighty less bendable.
This is an example of the type of silicon I will be using on this project.
This is the silicon material. The yellow is part A and the blue is part B.
I placed the 3D model of Drennan's foot into the bigger size of the fin. Because of the angle of Drennan's foot when I made the cast, it was hard to figure out where I needed to add the silicon becuase it would either end up in the toe or ankle end and not in the middle. I decided to add silicon to the toe end, so I sealed the ankle with duct tape so no silicon would pour out and angled the fin so that the toe would be up. I held that position in place with duct tape as well. To make the silicon, I added equal parts of both part A and part B into a cup and stirred constantly for 3 minutes while being sure to scrape the sides. I poured the mixture into the hole at the toe end.
This shows the seal I made with the duct tape so no silicon would leak out.
This shows the fin and the model after I had poured the silicon in. I colored it with blue dye.
As you can see here, a little bit of the silicon began to leak through the dct tape, however the material filled up to right around the top of the fin even with the leak.
The silicon had not dried fully becuase no air could reach the parts where the material touched the fin. This allowed it to slide nicely out of the fin.
Where there is blue material is where his foot does not fill in the fin. This is what he would wear over his foot to add up to the amount of the fin so he can wear it properly.
Because of the lack of material on top of the foot, the silicon is not going to be a sock, however it will be an insert. There is not enough material for him to wear it because the thin layer would rip and not stay on. The material will most likely stay in the fin while he will slide his foot in and with the material, it will be able to stay.
Reflection
Through this project, the most important lesson I learned was how to work with other people. That might seem shallow, however working on a project to help another person can be a very sensitive thing. Having another person come to you and propose an idea on how to make their life better can be extremely intimidating, so I am so grateful for Drennan and his acceptance to work with me. It adds another layer of pressure to your project as well. If something goes wrong and it doesn't come out the rght way or doesn't get finished in time, you are not letting just yourself down anymore. They have put their trust in you to possibly make their lives easier. The biggest problem I faced during this project was the positioning of the foot. The way I had Drennan's foot while making the cast was not exact to what his foot would be like in the fin. Therefore, it was hard to place the model in the fin and also to make the silicon fill in all the way around his foot. This is why the "sock" turned into an "insole".
I had Drennan test the fin insole and _____ (results pending).
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