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FMA Technology |
Design and Architecture |
Vacuum Inserter Tool |
Titanium Pedistal |
FAQ |
Pricing |
User Instructions |
Layout Specifications
FMA: Frequently Asked Questions
Arrays
Connectors
Implantation
Arrays
Can you make the microelectrodes to have different lengths within an individual array?
Yes, electrodes can be made to be any length between 0.5 mm to 10
mm long within an array. Use FMA Design Sheet to specify individual
lengths by position in the array.Back to top
Which metals may I select for the electrodes?
At this time we are offering either platinum/iridium 70/30% or pure
iridium as the electrode’s solid core conductors. Although tungsten is
slightly stiffer it is not considered by most investigators to be as inert
or biocompatible. Back to top
What are the impedance values of the electrodes?
Selectable impedance values may range anywhere between 10 kilohm
to 2.5 megohm depending on your application. Impedance values may
also be different for various electrodes within an array. You may also
choose to include an electrode with virtually zero impedance for
ground or common, which is an uninsulated electrode. Back to top
How large are the electrode tips?
Typically the microelectrode tips are between 2 to 3 microns for most
Platinum/Iridium electrodes. However, this value may be specified for
special applications. As an example, we are currently supplying pure
iridium electrodes for a visual prosthesis study that has a diameter
range of 5 to 6 microns. Back to top
What is the insulation over the electrodes?
The microelectrodes are insulated with Parylene-C, a biocompatible
polymer that has been successfully used for many years as the primary
insulator for countless implantable devices and electrodes. Back to top
Why do you show 2 electrodes with much longer lengths?
For FMAs requiring microelectrode lengths less than 2 mm we
recommend that at least 2 electrodes have lengths of 2.5 mm to act as
anchoring pins. The anchoring pins provide needed support to ensure
that the array remains securely anchored in the brain or spinal cord.
These electrodes are typically chosen to be the reference and/or ground
electrodes. Back to top
Can I use these arrays for either acute or chronic studies?
Yes, although the FMAs were primarily designed for long-term
chronic studies, they may also be used for acute studies where one
needs to insure that the array will float with the brain during recording
or stimulation protocols. If brain movement is not an issue,
investigators typically use our Multi-Electrode Arrays. Back to top
Can I select to have less than 18 electrodes?
Yes, 4 is the minimum number of electrodes that may be ordered
within a single FMA. Back to top
What is the tolerance of the specified electrode length?
At this time we can guarantee the specified electrode length to be
within 200 microns. Back to top
Can I reuse the arrays?
You can reuse an array used for acute studies. It is recommended you
clean the array in 50% bleach and distilled water. Chronically used
FMAs are typically not reused because of tightly bound connective
tissue around the FMA and cable. Back to top
Can I specify an array with less or more electrodes having a
substrate geometry different from the 1.95 x 2.45 mm size that is
offered?
Yes, you can specify different layout geometries that also require a
different number of electrodes. We have provided custom designed
ceramic substrates for customers. There is a one-time non-reoccurringengineering
(NRE) charge of $3800 to $7500 (typical) to have your
own layout and implant geometry designed for your particular
application. Inner electrode spacing must be within 250 to 1000
micron constraints. Please allow 2 to 3 months for delivery of FMAs
with custom designed ceramic substrates.Back to top
Connectors
Can you make the FMAs with different connectors?
No, at this time we use custom nano connectors made by Omnetics
Corp., designed for sonic bonding techniques needed to attach the fine
gold wires from the FMA. We may provide interface cables that can
be attached between the Omnetics A8141-001 type design of the FMA
and your headstage amplifier connector. Back to top
What are the available cable lengths?
Cable lengths may be
specified from 1.5 cm to 12 cm.
How can I minimize the cable tethering forces?
Putting a slight kink in the cable between where the cable exits the
bone edge and the implanted array will help provide necessary slack
during potential brain to skull movements. Also many investigators
have found that by applying a very small amount of highly viscous
biocompatible cyanoacrylate glue over the cable about 2 to 3 mm from
the implanted array and securing the cable to the pial surface, is very
effective in eliminating potential movement. Keeping the animal
relatively immobile during the first few days after implant is also
recommended. This assists in the natural encapsulation of the array at
the surface of the brain due to normal tissue adhesions that occur
around any foreign body implant. Back to top
What type of wire is used from the array to the connector?
We used 0.001” (25 micron) gold wire from the ceramic substrate
array to the connector. The cable is over-coated with MDX4-4210
silicone elastomer for flexibility and strength. Back to top
Implantation
What is the best way to implant the array?
The primary concern when handling the FMA prior and during
implantation is to insure that the microelectrodes do not touch
anything other than soft tissue. The microelectrode tips are very fragile
and may bend if the electrode tips are allowed to come in contact with
bone or any other hard surface. It is imperative that the
microelectrodes be implanted perpendicular to the surface of the brain
to insure minimal tissue disruption during insertion. We offer a
vacuum inserter system that is described in the User Instructions, which is the preferred method of inserting the arrays. Back to top
How fast should I insert the array into the brain?
It is recommended that the FMAs be inserted very slowly. The FMA
should be lowered until there is only a small amount of dimpling of the
brain. Allow the electrodes to penetrate the pial membrane before
advancing the FMA further. Slowly lower the FMA into the brain
stopping the advancement every few hundred microns to allow the pial
membrane to relax after insertion. The concept of this procedure is to
advance the FMA at a slow enough speed so as not to depress the pial
membrane, which will compress the brain, during insertion of the
electrodes. Back to top
Is their tissue damage resulting from the insertion?
Tissue damage is typically avoided by implementing the following
precautions. First, try to avoid placing the electrodes over any blood
vessels when initially positioning the array for implantation. It is
important to insure that the electrodes are as close to perpendicular to
the brain’s surface as possible before lowering the array into the brain.
And lastly, lower the array as slow as possible into the brain. Back to top
What parts of the inserter tool can be sterilized??
The tubing, including the inserter wand, may be sterilized; although in
most instances, it usually is only necessary to sterilize the tubing and
cannula extending from the wand. Back to top
Can I implant the array through dura?
It is possible to implant the array through dura for smaller animals,
although this is not advised for chronic studies. One reason for this is
that there maybe lateral relative movement between the pial and dura
membranes, which may cause the electrodes tips to move causing local
adhesions near the tip. Back to top
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