What if your watch face didn't stop at the top of your wrist? Maker Dan Chen built a wristwatch that wraps a ring of tiny screens around the whole band, and it's a great little lesson in electronics, wearables and 3D printing all at once.
The build uses eight small OLED displays lined up side by side, so the picture can flow around your wrist instead of sitting in one flat rectangle. The brain is a tiny ESP32 board, a cheap Wi-Fi and Bluetooth microcontroller that hobbyists love because it's fast, well documented and easy to program with Arduino tools.
The clever part is how all eight screens get their data. Small OLED modules usually talk over I2C, a two-wire connection where every device needs its own address. The catch: identical screens ship with the same address. Chen solved it with an Adafruit PCA9548 eight-channel I2C multiplexer, which works like a railway switch. The ESP32 picks a channel, sends that screen its image, then flips to the next one, fast enough that the whole band looks alive. He has already hinted at a second, more compact version.
Want to try something similar? Start small: wire two OLEDs to an ESP32 through a multiplexer and get each one showing different text. Next, measure your wrist and sketch a segmented band in your CAD tool of choice, with a pocket for each display and a channel for the wires. Print a test segment first and check the screen fit before committing to the full band. Flexible filament like TPU makes a comfortable hinge between rigid segments.
Try it on your printer
Wearables are where 3D printing really shines, because no store sells a case shaped for your exact project. Print a single display pocket in PETG, tune your wall count until the screen snaps in snugly, then scale up. Looking for filament, printed parts or inspiration for your next build? Visit Flarelab and let Flick the Fox point you to your next project.
Frequently asked questions
Why do you need an I2C multiplexer for multiple OLED screens?
Most small OLED modules share the same fixed I2C address, so the microcontroller cannot tell them apart on one bus. A multiplexer like the PCA9548 splits one bus into eight channels, letting you talk to each screen in turn.
Can I 3D print a watch case in PLA?
You can for prototypes, but PLA gets soft in a hot car and feels rigid on the wrist. PETG or TPU is a better pick for a wearable because they handle heat and flex better.
What print settings work best for a curved wearable enclosure?
Use a 0.4 mm nozzle with 0.12-0.16 mm layers so curves look smooth, 3-4 walls for strength, and orient the part so the outer curve prints without supports where possible.
Is an ESP32 powerful enough to drive eight displays?
Yes. The ESP32 has plenty of speed and memory for small monochrome OLEDs. The bigger limits are battery life and how fast you refresh all eight screens.
Inspired by this project feature on the Adafruit Blog. Project by Dan Chen. Rewritten for beginners by Flarelab.
