Making Electrodes

A good tutorial video on how to use a multimeter before making electrodes.

Extracellular Electrodes

• 1. 1. Plug the soldering iron in to heat it up and add water to the sponge in the soldering iron stand. Acquire solder (thin type) and flux in a small transfer pipet.

        • • • Make sure to wash your hands after using the lead solder and to wear gloves while using the flux!!

            • Test the soldering iron on the sponge; if sufficiently hot there will be a strong sizzling sound.

     2. Turn on the carbon filter fan and place it downwind of the soldering iron. *Do not breathe in the soldering fumes! Lead contamination!*

     3. Acquire 1 banana plug, 2 coated multiple-strand wires (use different colors so you can keep track of which wire is which) each 4-5 ft long, and 2 electrode wires (one for the electrode and one for the ground).

        • • • Twist the 2 coated wires around each other to prevent them from becoming a tangled mess down the line.

     4. Strip one end of both wires about 1/2 in. Feed the end of each wire around the banana plug and one end into each connection point of the banana plug. See the image below.

     5. Screw the wires into the banana plug connection points using the included screws. See the image below.

        • • • Make sure to put the screwdriver end of the screw outward or it is very difficult, nearly impossible, to remove the screw and invert it.

     6. Strip the other end of the coated wire about 1/2 in. 

     7. Wrap the exposed end of the stripped wire around one end of an electrode wire (normally stainless steel electrode pins or silver wire).

     8. Clamp the wrapped wires into the soldering stand on either side of where the join to be soldered is located. 

        • • • Make sure not to create a severe bend in the electrode wire or join when clamping the wires into the stand.

     9. Apply a thin layer of flux to the overlapping wires and wait ~30 seconds. Dab off the excess flux with a kimwipe.

        • • • Flux causes the surface of the metals to be soldered together to become porous, allowing the solder to create an electrical bond between the two wires.

     10. Touch the tip of the soldering iron to the underside of the overlapping wires and the end of the solder to the top of the overlapping wires.

         • • • The soldering iron will cause the wires to heat up and melt the solder.

     11. Apply a thin layer of solder to the entire length of the overlapping wires using this method. The overlapping wires should appear shiny when coated with a layer of solder.

     12. To remove excess solder from the iron, jab the tip (don’t scrap it) into the holder with the metal sponge. Then cleanse the tip of the iron with the wet sponge in the stand.

     13. Test the electrical connection by attaching a multimeter to the electrode wire and the corresponding side of the banana plug on the other end of the electrode.

         • • • Note: Make sure to unclip the soldered electrode from the soldering stand before testing the connection with the multimeter otherwise the reading will be unreliable.

     14. Slide a piece of heat shrink tubing over the wire–only long enough to cover the newly soldered connection. 

     15. Clip the electrode back into the stand and use the heat gun on low to gently shrink the heat shrink tubing so it’s snug on the wire/connection.

     16. Repeat steps 6-15 for the ground electrode with the other coated wire.

     17. Solder where the wire connects to the banana plug on each side to ensure a robust and protected electrical connection–don’t use flux for this soldering.

*Make sure to unplug the soldering iron and fan when done!! This keeps the soldering iron from burning out!*

Intracellular Electrodes

Suction Electrodes

What are suction electrodes and why would you use them?

Suction electrodes are extracellular electrodes that attach directly to the nerve via suction adhesion and can both record electrical activity and stimulate nerves. The electrode is housed inside a tubing exterior with saline to create an electrically isolated environment where it attaches to the nerve. Normally, to record extracellularly you’d make a vaseline well to electrically isolate the portion of the nerve you want to record from. However, if you have a preparation with intact muscle (i.e. an entire heart) you’d want to use suction electrodes. Otherwise, as the preparation’s muscles move they would destroy the vaseline well and the signal would no longer be electrically isolated.

Extracellular Electrode Construction

• 1. 1. Make an extracellular electrode following the instructions above.

        1. • • A good tutorial video on how to use a multimeter.

Making Suction Electrode Tips

1. 1. 1. Acquire a lit spirit lamp and small pieces of small-sized tubing.

      2. Hold the small pieces of the tubing over the spirit lamp so they start to melt in the middle.

         1. 1. • DON’T hold them close enough to the flame that they burn!

      3. Once the plastic starts to melt gently pull the ends of the tubing apart until they create a thinner tube in the middle and eventually break.

      4. Trim the newly created electrode tips until the diameter of the opening is the desired width.

Assembling Suction Electrode

Please refer to the images below to clarify the following description of the order of connections for the suction electrode.

• 1. 1. From the syringe end, a 5mL syringe is attached to a 3-way Luer-lock stopcock in the linear male end.

     2. Opposite the syringe (on the female connector for the stopcock) a 1/16” barb to the Luer lock fitting is attached.

     3. Then a length of Tygon (type E-3603) tubing (OD ⅛” ID 1/16” wall thickness 1/32”) approximately 12 in long is attached to the barbed end of the fitting.

     4. To the other end of the tubing, a T-junction with 1/16” barbs is attached via the perpendicular barb.

     5. The electrode wire is then fed through the linear portion of the T-junction while the ground electrode is left free.

     6. On the side of the T-junction furthest away from the soldered connection of the electrode wire a small (~1-2 in) piece of tubing is attached to the barbed fitting–the electrode wire running through the fitting.

     7. A previously pulled suction electrode tip is then threaded over the electrode wire and into the larger piece of tubing (to hold it securely in place)–appropriately trimming the suction electrode tip to a sufficient length so the electrode wire sits just before where the tip narrows.

     8. The join of the electrode and T-junction closest to the soldered connection is sealed against water damage with silicone (Gorilla Silicone Sealant) and left to cure.

        • The easiest way to apply the silicone is to hold the electrode wire on either side of the junction using the soldering stands’ alligator clips.

     9. The electrode is then affixed to a rod so it can be attached to the micromanipulator and used for experiments (*image to be added*).