DP1 Learning Portfolio – A Custom Designed Skin Barrier

Author: Bryan Peart (peartb)
Course: IBEHS 1P10 – Health Solutions Design Projects
Project: Design Project 1: GI Joe – The Endoscopy Unit
Team: Team 21
Role: Subject Matter ExpertPrototype leadVideo

My role: For this project I was the Subject Matter Expert. I designed, modelled and fabricated the prototype from start to finish (barring the first iteration), and produced most of the showcase video.

Skills

3D modelling & CADBlender sculptingGenerative design (Fusion)CAD modellingSee Prototypes 2 & 3, 3D model
Fabrication & prototyping3D printing in TPUAssembly & finishingLow-fidelity prototypingSee Prototypes 1–3
ResearchClinical case studiesOstomy form & functionSee The problem, What I learned
CommunicationFilming, directing & editingProduct photographySee Showcase video

Outcomes

Final prototype: black TPU barrier with an orange flange next to a beige snap-on pouch — **Fig. 1** Final prototype: TPU barrier with snap-on pouch

Final design: a wider (~1.5×), lower-gradient convex barrier shaped to the patient’s body, spreading the same force over more skin (P = F / A) [1]. Prototype
3 prototype iterations, ending in a 3D-printed TPU barrier with a working snap-on pouch.
CAD model of the final barrier. 3D model
2.5-minute showcase video. Watch

Fig. 2 Showcase video (2:29), filmed, directed and edited by me. It's a high-level summary of what we built, why we did it and a demonstration of how it works. The build is in section 4.

1. The beginning

Okay hello hello hello, welcome to my dp1 learning portfolio! :D

The following is functionally a summary of the project that is loosely in the form of a blog. Most of the content here is identical to what's covered in the video, but I'll try and dip a bit more in depth into what I did than I do in the video.

In the wise wise words of a man from Cambridge, Massachusetts:

“The only way to learn is by playing, to win is by learning, and to begin is by beginning.” So without further ado, let's begin.

2. The problem

Patient background: For this project our patient was Hurley, a colostomate. His stoma is retracted, so it sits flush with or even behind the level of his skin, when it should ideally protrude 1.5–2.5 cm.

The problem: A conventional convex barrier (Fig. 3a) caused a peristomal pressure ulcer. A flat barrier (Fig. 3b), which wasn't designed for retracted stomas, made it so that effluent leaks under the barrier [2], [3].

Compare:

Cross-section diagram: a convex barrier pressing into the skin around a retracted stoma so it protrudes — **Fig. 3a** A convex barrier presses the skin down so a retracted stoma protrudes into the pouch. For Hurley, that pressure is what caused the ulcer. (From Convatec [4])

The flat skin barrier from our kit, with a cut-to-fit centre hole — **Fig. 3a** A convex barrier presses the skin down so a retracted stoma protrudes into the pouch. For Hurley, that pressure is what caused the ulcer. (From Convatec [4])

We created the following need statement to encapsulate the issues he and others like him have:

Need statement (team): Design a custom orthotic for ostomy patients who have an increased rate of stoma retraction. Patients with retracted stomas who use convex skin barriers can experience discomfort and pain, while those who use a regular flat skin barrier experience greater risk of leakage [2], [5], [6]. The orthotic should both minimize the pressure on the site of the stoma and reduce the likelihood of leakage.

Constraints and objectives

Then we put together some constraints and objectives we have for a solution:

Constraints	Objectives
It must meet medical standards, must not leak, must not put harmful pressure on the peristomal skin and must attach to a waste bag.	It should be customizable to different stoma sizes, should be manufacturable at scale, should be affordable to the end user, should stay adhered even when in contact with other fluids, should function properly for 5–7 days, should not irritate skin that it is adhered to.

3. Concepts

Hand-drawn concept sketch: scanning the stoma, 3D modelling, and a custom-fit barrier that moves pressure around evenly — **Fig. 4** Concept sketch: 3D-modelled custom fit

Now that we had a framework through which we could analyze solutions, the team weighed three main concepts:

3D-modelled custom barrier

Pro Fits perfectly, spreads force, no cutting to fit

Con Cost, would need re-scanning if the body changes

Wider ring barrier

Pro Spreads force, cheap change to existing products

Con Takes up more skin, harder to apply alone

Inflatable ring

Pro Adjustable

Con Puncture risk, extra parts, pushes in every direction

4. My contributions: building the prototype

The prototype was my responsibility from basically the start to the end: the modelling (of the body), the CAD (of the part), the 3D printing in TPU, assembly and finishing.

Prototype 1 - Concept 1: Wider barrier

This first prototype was made as a team in the design studio while we were discussing concepts. We made it mostly to illustrate the ideas we were talking about to each other, but it ended up telling us a lot more than we thought it would.

Low-fidelity Prototype 1: a skin-toned disc with an orange model stoma in the centre — **Fig. 5** Prototype 1 low-fidelity model

After making and really considering this idea, we realised that expanding the barrier alone wouldn't be enough. If we stuck with just this, the increased size would make it hard for Hurley to move around, and the uniformity would mean we couldn't guarantee that a pressure point wouldn't form along a skin fold.

Prototype 2 - Concept 2: molding the part to the body

Front of the black TPU-printed barrier, showing the body-matched contour — **Fig. 6** TPU print: front

This iteration marked a shift in our design philosophy. Instead of an off-the-shelf convex shape, I sculpted the rough shape of a stoma and the surrounding tissue in Blender. I then used generative design tools in Fusion to build a barrier that is the exact negative of the body (± tolerances). This makes the barrier conform, preventing those aforementioned pressure points. I then 3D printed it in TPU so that we could get an idea of the flexibility.

Prototype 3: final prototype

This combined both ideas: a wider barrier (about 1.5× a standard barrier) in softer material that takes the exact shape of the body. It was built the same way as Prototype 2, but on a new base with more accurate measurements. This iteration also changed the materials. We realized that if we wanted to follow the contours of the body, we would need to seriously worry about the breathability and longevity of our materials. My teammates brought forward their final materials based on their research, and I integrated them into our design. In the prototype, the felt layers on the back of the wafer (Fig. 7) show the material stack-up:

Black: silicone elastomer backbone
Grey: hydrocolloid adhesive layer
Orange: ceramide layer to protect the peristomal skin

Back of the wafer: grey felt disc with an orange felt ring around the stoma opening — **Fig. 7** Back of the wafer: showing the felt layers that stand in for the changed materials

Hand bending the TPU barrier with the pouch attached — **Fig. 8** The attachment mechanism still works on our prototype

3D model

Open the interactive 3D model

For fun, here is the CAD model of the final prototype (Fig. 9). It is made of layers (backbone, adhesive and skin layers, and flange), about 12.6 cm across. You can rotate it, spin it, zoom in on it, or even separate it out into layers (but don't look too close, I ran out of time to paint the model cleanly :p).

Loading 3D model…

Drag to rotate

Fig. 9 Interactive 3D model of the final prototype

5. My contributions continued: the showcase video

Still from the showcase video: a hand pressing the barrier onto a model stoma — The full video is Fig. 2, at the top of the page

Another big component of the project I worked on was the showcase video (Fig. 2)! We had pretty much free rein to demonstrate our prototype and explain what it is.

I filmed, edited, and directed the video myself, taking advantage of the media rooms on campus. I am maybe overly proud of this part, but I had a really good time making it!

6. What I learned

Prototype early: This is one of those things that I hear people say all the time, but I never really understood until this project. When we built that initial prototype (Fig. 5), it genuinely changed our perspective on our issue and our solution, despite the fact that it wasn't remotely as high quality as any of our later ones.

Check check and check again: In contrast to that idea I think I also learned how important it is to validate the assumptions you make when you are trying to go quickly. Part of the changes made between prototype 2 and 3 was to readjust the underlying dimensions we were working off of. We needed to do this because in the interests of prototyping fast I didn't read the clinical data I collected critically enough. This led me to make errors in the design that could have invalidated any tests of the design as it wasnt reflective of an actual body.

The value of quality documentation: I have always been the kind of person to hide my rough work, when I am solving a problem my thoughts and process can be messy and I always thought that sharing them with others would be pointless. With this project though I think that I learned how recording all my work including the pieces that I think are worse, makes it far easier later to meaningfully communicate the decisions we made. If I had tossed all the prototypes that we made in the middle I wouldn't have been able to make this site, let alone make a video to explain our solution.

Next time/If we had unlimited resources

I would love to have used a real scan of a patient rather than a sculpted approximation from data.
I wish we could have tested the prototype more empirically with pressure sensing technology. We have sources and general evidence supporting our design decisions, but we never really got to compare meaningfully.
Finally I think that actually manufacturing the barrier in silicone rather than TPU would have been huge. We talk a lot about its material properties, but we never actually got an opportunity to experience them hands-on.

Sources

Show sources

Third Space Learning, “Pressure formula,” GCSE Maths. Accessed: Nov. 6, 2026. [Online]. Available: https://thirdspacelearning.com/gcse-maths/ratio-and-proportion/pressure-formula/
L. McNichol, T. Cobb, Y. Depaifve, M. Quigley, K. Smitka, and M. Gray, “Characteristics of convex skin barriers and clinical application: Results of an international consensus panel,” J. Wound Ostomy Continence Nurs., vol. 48, no. 6, pp. 524–532, Nov. 2021, doi: 10.1097/WON.0000000000000831.
United Ostomy Associations of America, “Types of ostomy pouching systems: One-piece, two-piece & accessories,” UOAA. Accessed: Nov. 6, 2026. [Online]. Available: https://www.ostomy.org/types-pouching-systems/
Convatec, “Convexity guide,” Guide to Ostomy Products. Accessed: Nov. 6, 2026. [Online]. Available: https://www.convatec.com/ostomy-care/guide-to-ostomy-products/our-technologies/convexity-guide/
Hollister Inc., “Convex skin barrier options,” Ostomy Learning Center. Accessed: Nov. 6, 2026. [Online]. Available: https://www.hollister.com/en/ostomycare/ostomylearningcenter/usingostomyproducts/convexskinbarrieroptions
J. Hoeflok, G. Salvadalena, S. Pridham, W. Droste, L. McNichol, and M. Gray, “Use of convexity in ostomy care: Results of an international consensus meeting,” J. Wound Ostomy Continence Nurs., vol. 44, no. 1, pp. 55–62, Jan. 2017, doi: 10.1097/WON.0000000000000291.