Learn How to Hide Capacitive Touch Buttons in Your 3D Prints

Most of the things you build will need some kind of interface through which the user can interact — let’s call it a “user interface,” or “UI” for short. The simplest kind of UI will usually consist of a few buttons and something to indicate status, like a basic LED. But attaching buttons to an enclosure isn’t always as easy as it sounds and buttons don’t always look good. A great alternative is capacitive touch sensing and John Phillips has an Instructables tutorial that will show you how to embed capacitive touch buttons directly into your 3D prints.

The demonstration in the tutorial is just a simple rectangular panel, but you can image the possibilities. If the thing you’re building has a 3D-printed enclosure, you can integrate capacitive touch buttons into that in a completely seamless way — literally. The outer surface can be smooth and free of any seams, if you like.

That is possible because capacitive touch sensing doesn’t require physical contact. You may have noticed that some capacitive touch buttons and even some smartphone screens will react because you physically touch them. Your fingertip getting close is enough to alter the capacitance by a detectable amount. For a microcontroller-based approach like this, you can adjust the sensitivity in the firmware to suit your design.

The microcontroller Phillips used is an ESP32 on a development board (specifically, a ESP32-WROOM-32 dev board). The ESP32 has built-in hardware for capacitive touch sensing, so it is a great choice. Most other microcontrollers with analog input pins can also handle capacitive touch sensing, but it may not be quite as easy as with the ESP32. Other than the ESP32, all you need is some copper tape and some wires.

As Phillips shows, you design the 3D model with a small cavity inside for the copper tape. Then add a pause in the g-code when the 3D printer reaches the top of that cavity, put in the copper tape, and resume the print job. Holes let you solder in the wires and you can then fill those with hot glue.

You could even take this further by using conductive filament instead of copper tape, if you have a 3D printer capable of multi-material printing. That would eliminate the need for the pausing and manually applying copper tape, while also increasing the design flexibility.

Whether you use copper tape or conductive filament, you can easily add capacitive touch buttons to your projects for a clean UI.