Hi! Thanks very much for your feedback.
Capacitive touch sensors only work reliably when there is a much larger ground area near.
Best design is the touch area surrounded by a ground plane (grounded to Arduino ground).
Yes, I had heard that, though in this case an actual physical touch is preferred given the nature of the application. However, in the future I was going to build what you are talking about, so I was curious because my current application only senses an actual physical touch and not proximity like I've seen. As you can see in the images above, upon an actual physical touch there is a strong response, but before that, there's no response. Is the ground plane what allows for the sensing of proximity and not just physical contact?