I have done a test with sensors:
I took a rounded floppy cable broken and I took a single wire, then I removed the plastic sleeve from the wire, and I took a single copper fiber, to use it as sensor:

I rolled the single wire around a polycarbonate bar, and I welded it to the circuit, then I temporarily fixed the bar behind a panel:

…and everything worked! 😀 (the wire must be very thin to work properly behind 5mm of polycarbonate, and this is the thinnest wire that I have found in my home)

To fix the wire to the bar, I must heat the wire near the edge of the bar with a soldering iron.

Here I’m pushing the hot wire in the edge of the bar: heat melts the surface of polycarbonate and the wire fits in the edge. After this, the wire is fixed within the bar.

A finished sensor:

For a mistake, I have ruined the bar, so i have to restart from scratch:

So, I cutted the bar, then I polished its edges and I drill the holes:

Then I have adjusted the joints for the sensor bar:

Then I restarted to fix the wires in the bar, with the same method said above:

Done! Now I must build a “chassis for the circuit”.