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  • Summary: Removing nylon for wire electrodes

    Thanks for all the kind responses to my original question. I have
    included the responses after the original post.

    Cheers,
    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,

    John

    [>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

    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
    rara@dlcwest.com


    +++++++++++++++++++++++++++++++++++++++++


    >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.

    Respectfully,
    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
    ============================

    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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