Since DEF CON 29 was a masks & vaccines required convention, I wanted to make something that would make it easier to introduce myself and remain memorable to people who otherwise couldn't really see my face. I designed this badge to do that, but also to serve as a demonstration to other of how several off-the-shelf modules can be used to make something cool with just a little software gluing it all together.
The full details of how it's all designed are available over on the GitHub page, but there were a couple of things I was really proud of.
The 3D printed case uses custom-designed compliant buttons that worked really well to give a nice spring while being easy to print and the whole things snaps together to make it easy to show people how it's designed. A magnetic clasp holds it to a shirt or lanyard and the small internal battery can last for several days because it can sleep between button presses after the display is refreshed since the e-Paper does not require any power to maintain its image.
The screens are also not static images, they are rendered from fonts, so they can be customized by just changing the text in the code. QR codes can also be generated directly in the code. An ESP32 was chosen since it has Wi-Fi capability so images can be uploaded directly to the badge and a cool webpage is included that allows you to adjust the black/red/white thresholds on your device.
To get the fonts I wanted, I also made a script to render them into the right bitmap to make them easy to work with on the device. I've used that code since for several other small projects and it helps make things a lot prettier than the default fonts that a lot of LCD libraries include.
I made about 10 kits and sold a couple, there was some interest but the expensive screen and the fact that I used off-the-shelf modules made them more expensive than a lot of folks expected. I did give a few to some close friends and another person said they were going to build a couple following the information from the repository! It's always a cool talking point when I take it to conferences and conventions though and it has served its purpose well.