Floating Microelectrode Array

Floating Microelectrode Arrays (FMAs)*, specifically designed for long-term chronic applications. They improve upon the benefits offered by a standard chronic array while also accommodating numerous, user-defined specifications. These arrays are exceptionally customizable and well-constructed.

FMAs simultaneously empowers recording from different cortical layers, sub-cortical regions and depths as a result of combining uniquely long electrode lengths of up to 10mm with the ability to offer multiple lengths within a single array.

FMAs are made with a laser-drilled ceramic substrate to accommodate the number of platinum/iridium or pure iridium electrodes desired up to 32 channels. The array is then tethered using a bundle of 25µm gold wires (~1/3 the diameter of human hair) that have been coated with a silicone elastomer. This assembly allows the rigid connection point to be situated away from the array itself, which permits the array to float with all of the movements of the brain.

The FMA is implanted using a reusable vacuum insertion tool that is designed specifically to hold the back of the substrate. This tool will work with the majority of available micromanipulators and enables the user to perform a very gradual insertion process that minimizes dimpling. After the desired depth has been reached, the dura can be secured over the electrode substrate with sutures.

To enhance your experience and results when using FMAs, we offer a breadth of compatible, high quality connectors, headstages, headstage cables, and commutators. You may also wish to explore other options in Plexon’s family of specialty electrodes, probes and arrays including our Microwire Array, U-Probe, or the advanced Thumbtack Probe.

Research labs around the world performing stimulation and recording studies in larger animals, like primates, have trusted custom FMAs for years. Your Plexon Sales Engineer is available to provide additional information and help you determine what might be the most advantageous FMA configuration to optimize your research.

FMAs are customizable with numerous options detailed in the table below. It may also be possible to produce arrays beyond the specifications listed. It is recommended that you discuss your needs with a Plexon Sales Engineer to determine if your unique request can be accommodated and/or the most ideal configuration for your research needs.

Feature Specifications and Options Remarks
Applications In vivo; chronic
Electrode material Platinum/iridium, pure iridium, or activated pure iridium Different materials may be used within a single array. Pure iridium is most often suggested for chronic stimulation studies.
Tip diameter 1 to 6μm Custom diameters available depending on application, however typical request is 2 to 3µm.
Impedance 10kΩ to 5MΩ Specified by user. Most users prefer all electrodes to have the same impedance with the exception of the reference and ground electrodes. Typical requested impedance for the reference electrode is 25kΩ.
Electrode count 4 to 32 Plus one additional for each of the reference and ground electrodes. Electrodes 4 to 16 utilize a single connector, while the higher counts require two.
Electrode length up to 10mm Exceptionally long lengths beyond industry norm of 1.0 or 1.5mm available and enable recording from different cortical layers and sub-cortical regions. Multiple lengths are possible within a single array enabling recording at different depths.
Inter-electrode spacing 400μm Custom spacing arrangements may be available, however at a high cost.
Reference electrode Available, but optional Typical requested impedance for the reference electrode is 25kΩ.
Reference electrode length 2.5 to 10mm The reference electrode is recommended to be 2.5mm for electrode lengths less than 2mm to act as an anchoring pin to stabilize the array after it has been implanted.
Ground options Electrode or wire
Ground electrode length 2.5 to 10mm The ground electrode or wire is recommended to be 2.5mm for electrode lengths less than 2mm. If an electrode, it also acts as an anchoring pin to stabilize the array after it has been implanted. If a wire, that length is useful for wrapping around the skull screw.
Array dimensions 16 channel array:
1.95 x 2.45 x 0.50 mm
32-channel array:
1.80 x 4.00 x 0.50 mm
Wire bundle/cable length 1.5 to 20cm Estimate an additional 15% length necessary for providing a slight “kink” in the cable for strain relief.
Wire bundle/cable material Gold wires covered with a silicone elastomer
Wire diameter 25μm
Connector count Single or double
Connector type CON/16o25m-18P
For more information on these connectors, see the connectors page.

*FMAs are manufactured by MicroProbes for Life Sciences.