Capacitive touch sensing allows for triggering the sensor without actually physically touching one’s lips to the electrodes, which [Nathan] did by putting a clear plastic layer over the PCB traces.

My PCB "business card" was designed with a credit card sized form factor in mind to easily fit into a wallet. The board also doubles as an ATtiny85 development board with pins broke out and a ...

Tom Fox has created a capacitive touch sensor using a Raspberry Pi Pico that makes use of all 26 pins with his custom PCB he calls Spoke.

He ended up building a little doohickey that combined USB C, an LCD display, and a touch interface, all for under a buck. You can check out the video below. The key to this build was the CH32V003 CPU.