Banana Exoskeleton
Every banana is different.
Bananas bruise easily, so people carry them in cases.
Mine kept going soft at the bottom of my backpack.
“I found a banana that fits perfectly in my banana case!” A post on r/oddlysatisfying.
“The case sets unrealistic standards for bananas.”
A reply under it, with 8,200 upvotes
Can one case fit any banana?
A two-person class project for Computational Methods for Interactive Systems at Carnegie Mellon, spring 2025
So I designed the
Banana Exoskeleton
A 3D-printed case that bends to fit the banana inside
It opens along its belly, then closes around the banana.
The Ring by BØDEX, one of the compliant mechanisms I printed and tested.
Its trick is a compliant mechanism,
a part that moves by bending, with no hinges.
107 of them, levelled and scaled to the same width.
There was no dataset of banana shapes, so I built one.
1,400 bananas from photo libraries, cut out with YOLO and edge detection, then traced
I wrote an optimizer that bends a ring until it fits them.
It starts as a circle of points, and each step moves them to lower the energy, until the ring hugs the bananas of one shape.
The ring, its optimized outline, and the case.
Then I turned the outline into a 3D case, fully parametric.
Built in Grasshopper. Two rows of ribs grow from a spine along its back; the spine on its belly slides, so the banana goes in and the case bends with it.
Each cluster's bananas overlaid, above the case made for it.
Three cases cover the three most common banana shapes.
K-Means clustering found six shapes in the data. The three most representative each got their own case.
All bananas are beautiful.
- Role
- Ideation, data collection, computer vision, shape optimization, parametric 3D modeling, 3D printing
- Team
- Xinyi Luo
- Course
- Computational Methods for Interactive Systems, Carnegie Mellon University, with Alexandra Ion
- Tools
- Python, OpenCV, YOLO, K-Means, Rhino, Grasshopper, PLA printing
- Year
- Spring 2025