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[on:]

Hi all,

Just testing the water to see if there are any experts on this subject.

Rubber normally has a resistance in the mega ohms.  I know that you can 'mix in' graphite to make the rubber more conductive.  Could you do this to give the material a resistance in the same order of magnitude of a semi conductor such as silicon?  Is this possible without grossly changing the properties of the material?

Are there other cheap mouldable materials with conductive properties?

with thanks,

kenneth

[Reply #1 on:]

You might like to search the instructables site. I saw a project there that had all sorts of information about adding stuff to silicon to make it conduct.
As you might expect the more stuff you add the lower the resistance and the more affect it has on the properties.

What are you planning to do with it?

[Reply #2 on:]

There's this.

[Reply #3 on:]

What exactly to you mean by "Rubber"?

Do you mean natural rubber, or are you talking about elastic polymeres in generall?

There are conductive elastic polymers. I believe that you can find them in some remote controlls or keyboards as the buttons (though I personally have not followed that up yet, I am not 100% certain about that.) The thing with conductive polymers is that they will change resistence depending on the stress you put on them - if you google stretch sensors, most stretch sensors you will find are made of conductive polymers.

I have no experience with making my own rubber, though I have tinkered with silicone and electronics...

I think if you explain in a bit more detail what you plan to do, we might be able to give better advice.

p.

[Reply #4 on:]

Thank you for your replies.  My proposed project in more detail:

I'm a doctor with an interest in improving simulation technology and physiological modelling.  Medicine is increasingly moving towards simulation for training and our mannikins have a 'rubber' skin.  I don't know exactly what materials these tend to be except that to an untrained eye we would say that the material is rubber.

We attach ECG electrodes to patients to monitor the heart, but in simulation we attach them to little metal clips which protrude through the skin of the mannikin.  This is unfortunate as the ECG signal is extremely dependant on lead position, and this realism is lost.  I have created a programmatic way of generating the potential over the skin in 3d vectors.  If I could find a way of replacing the mannikin skin with a semi conductive skin then I could allow placement of ECG electrodes anywhere on the mannikin with different resulting ECG signals just like real patients.

Mowcius, your link showed an elastic polymer with resistance dependant on it's stress.  Metals already do this, this is how blood pressure tranducers work in theatre.  I can't see what advantage they have over a metal wire, but it would suffice.  Are they expensive?

kenneth

[Reply #5 on:]

Mowcius, your link showed an elastic polymer with resistance dependant on it's stress.  Metals already do this, this is how blood pressure tranducers work in theatre.  I can't see what advantage they have over a metal wire, but it would suffice.  Are they expensive?

Well I was guessing without knowing the application - it would not be suitable for what you're wanting to do.

A two part silicone rubber mixed with fine iron filings or similar sounds like the best way to go - I don't have any experience with this though so I can't advise.

[Reply #6 on:]

Yesterday, I did a search on conductive gels (TENS, ECG, EKG, etc), as part of this post:

http://arduino.cc/forum/index.php/topic,63549.msg463599.html#msg463599

One thing I found in my searching is that many of these gels are made using silicone gel (probably similar to the anti-scar silicone gels you can buy) with silver chloride mixed in to make them conductive (and likely none-too-cheap). One other thing I found (but didn't pursue) was a source of conductive silicone sheeting. I would imagine this is probably made with something similar to the common silicone sealant/glue you can purchase at a hardware store, with silver chloride or other compound mixed in to provide the conductivity needed.

I wouldn't be surprised if there isn't a source for such a "brush on" conductive material (once again, it isn't likely to be inexpensive - and you might have to purchase it in large amounts - think 55 gallon drum)...

[Reply #7 on:]

This is the thread I was thinking about:-
http://www.instructables.com/id/Conductive-Glue-And-Conductive-Thread-Make-an-LED/step1/Make-Conductive-Glue-Conductive-Paint-and-Conduc/

[Reply #8 on:]

Hi,

I have been playing around with conductive fabric and smart materials from this Educational website:


http://www.mindsetsonline.co.uk/index.php?cPath=16_574

They have a conductive lycra which I havn't tried but looks interesting. Maybe it could be incoporated into a matrix of natural latex rubber solution, the type you get from arts and craft suppliers

[Reply #9 on:]

This site seems to give a good indication of what might be available

http://www.emiconductiverubberllc.com/conductive-rubber-sheets.php

I would think what you are looking for is already out there somewhere.