st3f0:
I also tried that stripe geometry, that wvmarle suggested. I used a standard stripboard for that. I did not get it working, but maybe I did not get exactly how this was meant. Could you please clarify this, wvmarle? Should the stripes be alternately connected to the measurement electrode and to ground? Or somehow different?
No, my idea is to cut it so you have two parallel strips left. Nice and small, like your parts. Makes it easier to get the sensors small enough.
A bunch of alternating strips indeed doesn't work. I tried that myself.