Hi Everyone,
I need your suggestions on best resistive/conductive material which has following properties to be used as a exposed to human body potentiometer:
As an example, I recently tried 3d printing a thin sheet using conductive PLA spool but my problem with that was lack of resistance linearity across the sheet.
I appreciate your responses,
Can you tell more about your project ? What are you going to make ?
Something with a flat surface and X, Y coordinates ?
You have high demands ! And that's not all. Should it also be corrosion proof ?
How did you measure the resistance ? You could drill tiny holes in it and use tiny screws. That will make good contact.
Sometimes a simple copper wire or copper sticky tape will do.
You can get copper clad fiberglass sheet as thin as you like. Think printed circuit board material. That would fit all your requirements, as stated, with no other parameters being given.
Paul
Bit of an "XY Problem".
Copper will tarnish over time in contact with sweat. May or may not be a problem.
Come on now, give us a proper explanation> 
Many metals would fulfil that list of requirements, but I suspect you want lower conductivity than that.
Do you want isotropic conductivity?
Then there is the possibility of roughing up the surface a bit and coating with graphite powder. That would work on plastic sheet. But who knows what the OP has planned.
Paul
Thanks Koepel,
The goal is to build a violin/ cello fingerboard sensor.
Thanks Paul,
The goal is to build a violin/ cello fingerboard sensor so the copper clad does not seem a number one option.
Hi Mark,
Yes exactly, low conductivity is reasonable here.
That's right. Tarnish is a problem. The goal is to build a violin/ cello fingerboard sensor.
What are you trying to sense? Have you measured the resistance of finger tips after they have been playing a violin/cello? Bet they are completely dry and have VERY high resistance.
Paul
Sorry that was not clear enough. Violin/cello strings are part of the circuit. So sensing happens when string touches finger board. Something like what you see in the image:
I think trying to use a resistive sensor is the wrong way to go. It will, in my experience never be consistent enough. But if you want to try then look at a linear “soft pot”. See Soft pot
I think you would be better off with one or several of these.
https://bela.io/products/trill/
The long thin ones can be mounted end to end.
I recently made a MIDI guitar with two of these sensors, although I did divide the fretboard into frets in software rather than a continuous sensor.
Video at
https://www.youtube.com/watch?v=-22KG11FD_s
With part 2 here
https://www.youtube.com/watch?v=geYLBfoKyAM
The strings are conductive then?
As this is a linear application isotropy presumably isn't a requirement, so I'd suggest carbon fibre, although its pretty conductive its less conductive than metals.
With fingers involved you have the problem that the circuit includes a human, so the low impedance may actually be of benefit in rejecting inteference from the finger.
You keep saying this so I measured my carbon rod.
Resistance measured my touching together the meter’s leads 0.7 ohm.
Resistance measured with leads connection either end of a 3mm Dia 200mm long carbon rod 3.6 ohms.
Conclusion - carbon rods are useless for measuring the distance along it a touch is made.
Hi Mark,
Thanks for your response,
I tried that. Carbon fiber is not resistant enough for this job.
Hey Mike,
You are right about trill sensors in terms of consistency, I've got one of them. but forming these sensors as a real violin/cello fingerboard regarding curves etc., seems impossible.
I watched your videos, Awesome work!
Can the string itself be the resistance you are looking for?
Yes, but we have to build such a resistive/conductive string. That does not exist commercially. Metal violin/cello strings are fully conductive.
Did you try the new flexible one?