The Teensy 3 and Teensy LC have several pins that can be used as capacitive touch inputs.  I designed this board in KiCad to experiment with cap touch buttons:

Teensy LC cap touch demo

I used the CAPSENSE_CIRCLE component and footprint from the Wickerlib KiCad library to create the cap touch buttons:

source: https://github.com/pdp7/teensy-touch/tree/master/hardware

source: https://github.com/pdp7/teensy-touch/tree/master/hardware

source: https://github.com/pdp7/teensy-touch/tree/master/hardware

Bill of Materials:

• Monochrome 0.96″ 128×64 OLED graphic display
• Teensy LC, OSH Park edition

GitHub

• Repo: teensy-touch
• File: teensy-touch.kicad_pcb
• Commit: 5fb2f44 connect GND pin for OLED to GND plane