Metal Microelectrodes Basics
Superior microelectrodes for outstanding extracellular recording — tungsten, iridium, platinum-iridium, and Elgiloy®
WPI offers a large variety of metal electrodes and they come in three basic styles (profiles). The selection guide that follows references the three electrode profiles. In addition, concentric bipolar electrodes are also discussed, as well as some of the options offered for the metal electrodes.
NOTE: The electrode diagrams below are not shown to scale.
Concentric Bipolar Electrodes
These electrodes are excellent for shielded macro recording, as well as evoked potentials. They are especially well suited for bipolar stimulation. The tungsten electrode is sharpened to a point and is 75μm in diameter. The outer stainless steel conductor is insulated with Polyimide tubing to within 0.2mm of the end of the stainless steel tube. This electrode is also available without the outer Polyimide insulation.
This figure shows an insulated metal conductor with an exposed concentric surface.
Metal Electrode Options
Exposed Tip Dimensions (nominal)
WPI electrodesmade from a variety of metals and tip diameters to offer the nominalimpedance ratings you require. Use the table below to determine whichtype of electrode will meet your criteria.
Kapton (KT) Tubing
Kapton* tubing, indicated by “KT” in the part number, extends from the connector to within 5mmof the tip, providing stiffness and additional insulation to the electrode shaft. Kapton-
clad electrodes are recommended when the electrode is to be inserted through a cannula for extra deeppenetration.
Heat Treated Tip
The Heat Treated Tip (see image below) is ideal for penetrating tough membranes. (It is not recommended for chronic implantation.) This process is performed using a microforge in which the heating element is positioned in close proximity to the tip in order to melt the Parylene-C distal to the exposed metal. It provides a smooth transition and produces better adherence of the Parylene-C to the metal.
Both the KT and non-KT electrodes are heat-treatable. The heattreatment is applied only to the parylene coating. The heat melts the paryleneso it feathers down close to the shank near where the tip is exposed. This removes the abrupt edge where the parylene has been removed tocreate the tip exposure. The purpose is to prevent the parylene fromdelaminating from the electrode during implantation into tissue which couldcatch on the edge. Heat treatment does not work well in chronicapplications, because the feather edge is susceptible to fluid intrusion overtime, which will alter the impedance characteristics of the electrodeunfavorably.
To have your electrodes heat treated, just add the suffix “H” to any of the “KT” numbers on the facing page. This treatment incurs an additional cost. Please call for pricing.
* Parylene is a trade mark of Union Carbide. Kapton is a trade mark of DuPont. Elgiloy is a trade mark of Elgiloy Ltd.
Gold Plated Pins
Gold-plated pins (WPI #5482) and sockets (WPI #5483) may be attached to 24-, 26- or 28-gauge wire.
|300102||Micromanipulator holder, 4 in., 2mm to 0.031 socket|
|5468||2 mm receptacle to 0.031-inch jack (for Omega-TipZ|
|5469||Adapts mini banana plug (DAM80) to 0.031-inch receptacle (metal microelectrode)|
|5470||0.031-inch jack, 28 ga. wire, 12 inch (pkg of 4)|
|5482||Pins, 0.031-inch, gold-plated (pkg of 50)|
|5483||Sockets, 0.031-inch gold-plated (pkg of 50)|