anyone that has ideas to improve my DIY FSRs( Force Sensing Resistors)?

Hi guys,

if you know FSRs, you know they are really expensive. If you need just one, maybe you'd better buy a professionally made one. But if like me you needed more than 10, well price becomes an issue.

I have an idea on how to make cheap FSRs that I tested a couple of years ago (you can check out this project for the implementation https://hackaday.io/project/1601-diy-usb-midi-controller-mpc-style , project linked just for reference, not for extra likes). 

The cheap and dirty version is to just take a copper pad (like a square cut from copper tape, like the one Adafruit sells), stick (solder) a wire to it, put some antistatic black plushy thing that you find in IC boxes (the thing is the same as velostat), put another copper contact with a wire on it (like a sandwich basically) and seal everything together. If you need it to work as an open circuit when not pressed, just leave an air gap between one contact and the antistatic material (like a little frame, for example a couple of layers of adhesive tape on the sides of one contact should work fine).

Since I did not like having two separate layers of copper to make one FSR, I tried using a PCB, and it worked fine.

The idea is to have interdigited contacts laid out on a PCB, then have a sheet of plastic with holes above the contacts, and another sheet of plastic with Velostat pieces where the contacts are. The sheet with holes works as a spacer, that is to leave an air gap between the velostat and the contacts.

The problem with this approach is that I could not find an easily available glue that works well with Velostat so the sensors will eventually fail when the adhesive does not work anymore.

I might need these for a project I want to make in the near future and I was looking on ideas to improve this design. 

For example, I was thinking of using a laminator to properly stick together the spacer, the velostat contacts and the cover, but I don't have one at hand and I don't knowif it will work or not.

I also think that the best would be to have custom made rubber pads with velostat contacts underneath each pad; this would be the cheapest way because you would just need a PCB with the contacts and the custom rubber pad to put on top of it, but I have no idea how to source these, and even if I could find someone available to do them I don't think they would make one-offs, I would have to source a lot of them.

So, does anyone have a better way of laying little velostat pieces on top of the contacts made on a PCB, a way that is reliable and repeatable? Or does anyone know a fab that could make custom rubber pads with velostat implants underneath them? Anyone that worked with rubber knows if it is actually feasible to mix velostat and rubber together? Finally, is there an actual need for these that would justify an eventual crowdfunding project to actually start making these rubber pads? 

Extra: do you think Intersil/Sensitronics would get pissed off about such project? I don't know if these things could be open-sourced given the patents they have in place.