View Full Version : Summary: Removing nylon for wire electrodes

Eric Thomson
10-08-2000, 09:46 AM
Thanks for all the kind responses to my original question. I have
included the responses after the original post.

Eric Thomson
Department of Neuroscience
UC San Diego

In my initial post, I wrote:
I have some very fine nylon-covered stainless steel wire (48
gauge). Are tweezers best for removing bits of nylon, or are there other
tricks of the trade? In particular, I want to be able to make wire
electrodes with one tip exposed and the other wire exposed en passant (as
found in Scott and Thompson (1969)). Are there any chemicals which I can
use to remove the nylon? If you suggest heat, will the residue from the
oxidation process affect the results? If so, what can I use to remove
that residue?

Scot, RN and Thompson, GB An improved bipolar wire electrode for
electromyography, Med & biol Eng 7:677-8.

I received the following responses:

>From jbarden@ualberta.ca Mon Oct 2 15:36:09 2000
From: John Barden

Dear Eric:

I am currently performing a fine-wire EMG study of various shoulder
muscles. I make my own fine-wire electrodes and I use a clamp soldering
iron to burn off the insulation at both ends of the wire. This works very
well and allows good precison for measuring and standardizing the amount of
wire bared at the tip (i.e., from the end that records the signal from
within the muscle). Sandpaper also works but does not allow very good
precision with respect to how much of the insulation is removed. I haven't
tried any other methods and have not encountered any problems with using
heat. I hope this helps. Best of luck and let me know if I can be of any
further assistance.

Best wishes,


[>I responded:
>I'm embarassed that I'm not sure what a 'clamp soldering iron' is: is it
>different than a regular soldering tool (the heated conical metal tip)?]

Dear Eric:

No need to be embarrassed, I didn't have a clue what one of these things
was either until I started working on this project. I'm not even 100% sure
that the proper name for this thing is a "clamp soldering iron" (I'm 95%
sure - that's what everyone in our lab calls it). The one we have here
comes from Pace Incorporated and is called (this is what's written on the
side of it) a SensaTemp II "ThermoTweez". The best way to describe it is
to say that it kind of resembles a large pair of tweezers or a small pair
of tongs (ours is approx. 6 in. long - I have no idea as to what it's
intended use might be). It is a soldering iron that has two ends (two
small tips). I grab the wire between the two ends and then pull the wire
through. A couple of pulls through with the wire is usually enough to
remove all of the insulation. It takes me approx. 30 secs. to bare both
ends of a wire. The wire I'm using is from California Fine Wire Company
(it says size = .002 on it - not sure what gauge this is, pretty sure it's
the smallest they make). I hope that answers your question. Let me know
if you need anything else. Good luck.


John M. Barden, M.Sc.
Ph.D. Candidate
Surgical-Medical Research Institute
Department of Surgery
Faculty of Medicine & Dentistry
University of Alberta
Edmonton, Alberta
Canada T6G 2E2

Rehabilitation Technology Department
Glenrose Rehabilitation Hospital
10230-111 Ave.
Edmonton, Alberta
Canada T5G 0B7
Work phone: (780) 471-2262 ext. 2688
Home phone: (306) 924-0727
e-mail: jbarden@ualberta.ca


>From glennwms@UDel.Edu Mon Oct 2 15:36:13 2000
From: Glenn N Williams

Please forward your results t this question to me, as I am also interested
in this issue. I have used 50 micron wire with nylon for a while. I have
been burning the nylon off without any apparent ill effects on my results.
If you over heat, you will weaken the wire, but if it is quick and the
flame never touches the wire, its seems to burn clean and keep its
strength. I have never had one break in a subject. As for oxidizing, I
am well aware of this from my reading; however, I have never seen any
evidence on the wire - it appears to burn clean. Basmajian and DeLuca's
Muscle's Alive uses burning of nylon in their fabrication technique
example, so at least one classic reference has recommended it. I found
that stripping the wire with a scalpel or other instruments resulted in
the wire curling like a ribbon (for a present). As a result, it is
somewhat difficult to get a firm, standard length barb on the wire. Some
books recommend using a chemical stripping agent because it has no
mechanical effects on the wire and is less likely to oxidize it (eg
Electromyography for Experimentalists); however, the context of most of
these is with animal studies. I would need to be absolutely sure that
whatever material I was using to strip wires for insertion into humans was
removed when I sterilized them. I imagine that it would be, but would
want to see something concrete before using that technique.

Glenn Williams

Glenn N. Williams, PT, SCS
Biomechanics Laboratory
Center for Biomedical Engineering
126 Spencer Laboratory
University of Delaware
Newark, DE 19716
Phone: (302) 831-6704
Fax: (302) 831-3619
E-mail: glennwms@udel.edu


>From lmclean2@IS.Dal.Ca Mon Oct 2 15:36:15 2000
From: Linda McLean

Hi Eric,
You can order "conformal coating stripper" [a chemical stripper]
from most electronic component catalogues. (I got mine from Medtronic,
but it is made by M.G. Chemicals in New York : 716-667-3471) It
shouldn't damage your wire, but should easily remove the nylon insulation.
To be sure that the wire is not affected, I would examine it carefully
under a microscope and test it with current to make sure it hasn't
corroded. Your department of Chemistry can also probably make you up a
stripping solution that doesn't damage the wire.

They also make pens so that you can isolate the removal of the insulation,
but I actually find that I am more accurate with a tiny syringe. The key
is to try to make your pick-up (uninsulated) area identical on both wires.

Good luck!

Linda McLean
Asst. Professor
Dalhousie University
School of Physiotherapy
5869 University Ave.
Halifax, NS
B3H 3J5
(902) 494-2822 (Office)
(902) 494-1941 (Fax)


>From cap@ntrobotics.com Mon Oct 2 15:36:28 2000
From: Chuck Pell

This trick works on most insulated wire (even the smallest diameters):

1. Use a binocular microscope, fresh Exacto blades (No.11), and steady hands
2. Cut through slowly --- do not contact the wire with the blade --- by doing
the following:
3. Gently roll the wire with the blade, cutting the nylon in compression,
against a flat glass plate
4. This should take several rotations
5. Then --- barely before you are completely through the nylon --- use slow
tension to pull last tiny bit of connecting nylon off (This technique
prevents scoring, and thus the later breaking of, the 48 wire)

Remember that stainless steel "work hardens" when strain cycled and so should
*not* be bent (excepting only when absolutely necessary for the protocol)

Good luck,
Chuck Pell


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