mpr121 + teensy 4.0 cap sensing

Hey everyone,

I'm currently working on a project that involves using a Teensy 4.0 microcontroller with an MPR121 capacitive touch sensor breakout board. My goal is to achieve reliable touch sensing through approximately 5mm of plastic material, with an additional 0.3+mm of air on top of it. However, I'm facing some challenges with sensitivity and interference.

I've noticed that the MPR121 is barely sensitive enough to detect touch through the plastic layer, but it's being affected by external factors such as slight shaking or wind. I've also got a CD4051BE multiplexer available, but I'm unsure about how to properly set it up in a way that would improve the touch sensing capabilities.

My sensing pads are 0.1mm thick pure copper plates that are sized to about 26mm x 45 mm.

Keep in mind, I am still a newbie, so I am not too sure if everything I am doing is right

Is there any idea what I can do to improve the touch sensing?