A sophisticated neural interface that is typically best suited for chronic recording and/or stimulation in large animal cortex, the FMA has also seen successful use in a variety of small animal and peripheral nerve studies. The low profile, small size, and great flexibility of the FMA make it ideal for the implantation of a large number of arrays simultaneously in the same animal, allowing a multitude of cortical locations to be targeted at the same time. Additionally, the length and impedance of individual electrodes within the same array are completely customizable, giving researchers the capability of recording multiple cortical layers and deep structures, or collecting LFP and single unit activity from the same cortical region. The FMA is also capable of remarkably long periods of chronic use, with over seven years of continual single unit recording having been reported from multiple arrays in non-human primate.
- Up to 36 channels per array.
- Custom impedance in each microelectrode.
- Custom length of each microelectrode of the array.
- Custom pedestals.
- Microelectrode impedance is individually customizable from anywhere between 10 kΩ to 5 MΩ.
- Small, low profile arrays allow many to be implanted into one animal (over 20 arrays in primate).
- Available in Platinum/Iridium and Pure Iridium, with activation of Iridium electrodes on request.
- Cable length up to 20 cm.
Single Unit - LFP
Peripheral Nerve Blundes
The Floating Microelectrode Array FMA is based on the concept of a lightweight platform populated with rigid microelectrodes and tethered to a nano connector by a thin, flexible and light-weight cable. The platform which houses the individual electrodes is fabricated from 125 micron thick alumina ceramic, and has 18 or 36 evenly distributed holes with 250 or 400 micron separations.
FMAs can be fabricated with varying electrode depths not typically achieved using planar silicon technology. Current fabrication techniques allow for individual electrode depths between 0.5 and 10 mm. Impedance values for individual electrodes within the array may be specified from 5.0 kilohm to 2.5 megohm.
The cable is fabricated from Parylene-C insulated 25 micron diameter gold wires, which are wound in a helix for maximum flexibility and strength. The entire cable is insulated with a thin coat non-restrictive silicone elastomer, ensuring biocompatibility, flexibility and strength.
Chronic FMA Assemblies
The array shown above is tethered by eighteen fine wires, 0.001" (25-micron) in diameter, about 1/3 the size of a human hair. The gold wires are micro-welded to the shaft of the microelectrodes at the specified distance from the tip in order to establish the proper length of the electrode. The wires are sonically bonded to an Omnetics connector, which is used by leading headstage amplifier suppliers including Plexon, Ripple, TBSI, and Alpha Omega. These connectors have worked very well for other chronic electrode designs and are small enough to be used in mouse experiments as well. We offer optional titanium pedestals that will house a single Omnetics connector, and are currently developing pedestals that will house up to 6 connectors.
It features higher electrode density, reduced spacing between electrodes from 400 to 250 microns. It also has a smaller substrate size.
FMA Length Options
The VIK-2 vacuum insertion kit features a selection of accessories necessary for the handling and implantation of Microprobes for Life Science Floating Microelectrode Arrays (FMAs). These arrays feature very small and low-profile heads that are challenging to safely grip using traditional manipulators and clamps. Instead, the VIK-2 employs a benchtop electric vacuum connected to a blunt-tipped needle that acts as a miniature vacuum tweezer for the array. This probe can be easily mounted onto a variety of stereotaxic holders, providing a universal solution.
This kit includes everything required to equip your stereotaxic holder with vacuum capabilities, including the pump itself, large ¼” tubing, thin flexible 0.07” PVC tubing, ¼” to luer lock adapters, three-way luer lock stopcock valves, and an assortment of five different gauges of blunt tipped needles for a variety of implant sizes and surgical solutions. For those that already have a vacuum system and just need the thin tubing and accessories, see VIK-2A vacuum insertion accessory kit.
- Powerful medical-grade vacuum aspirator pump capable of wet or dry operation.
- 800ml in-line aspiration bottle that can be removed and cleaned independently.
- Strong and quiet operation: >40 LPM flow, 560 mmHg, <58dB, AC 115V, maintenance-free.
- Built-in pressure gauge and regulator valve.
- Convenient carry handle and base featuring rubber vibration-dampening suction feet.
- Replaceable bacterial filter prevents contamination of operating space.
- Included stopcock valves allow vacuum to be conveniently controlled at the holder, allowing for quick purging of tubing to safely release the array.
- Kit includes accessories to allow multiple vacuum tips to be employed simultaneously from the same pump.
VIK-2A Vacuum Insertion Kit Accessories
The VIK-2A is a stand-alone package containing the accessories already included in the VIK-2 vacuum insertion kit, only without the included pump. This accessory package is great for users who already have a vacuum system and just need the adapters and accessories, or for those who have a VIK-2 and require additional or replacement parts.
The kit includes:
- (3) 0.07” PVC tubing, 10”, luer lock ends
- (3) Three-way stopcock valves, luer lock
- (2) ¼” to luer lock hose adapters
- (10) blunt-tipped needle assortment, 1” length, five sizes
Microprobes for Life Science Large Animal Pedestals are precision machined using durable materials incorporating a design that has evolved from feedback received from many experienced investigators. Our new pedestals provide safe, stable, and low impact performance. Each one is custom fabricated and constructed of pure milled titanium with a smooth surface finish.
The single-housing acrylic anchored pedestal incorporates a silicone gasket and titanium lid to prevent moisture and airborne debris contamination. The 1.7mm diameter flanges, extending one from each side, allow for easy fixation of the pedestal to the skull using cranial cement. Pedestal sizing is available for both 18 and 36 channel Omnetics nano strip connectors. The multi-housing Crist Instruments Pedestals feature a low profile Ultem cap secured using side-mounted set screws, and six reinforced anchor points sized for standard large-animal skull screws. All pedestals are available with one of three lower contour options: flat bottom, curved bottom, or custom cut using researcher-provided topographic imaging to precisely match your implant location. These pedestals feature a scalable architecture allowing for one to four standard Omnetics nano strip connectors of either 18 or 36 channel size.
- Precision milled titanium body provides light weight, high strength, and MRI compatibility
- Side-mounted cap set screw keeps vertical profile low and minimizes thread stripping
- Compatible with all Microprobes for Life Science flexible cable arrays in any combination
- Six reinforced anchor points provide a stable mounting on all sides
Single Housing Pedestal
|Connector Type||Description||Acrylic anchored
|Screw anchored (including six skull screws)
|Screw anchored (Pedestal only, no screws included)
|A79038-001||Male Omnetics connector - 16 channel, 18 pin, 0.025" pitch, 2 guide posts, two rows||IP-20-038||CP-20-038-SC||CP-20-038-00||Footprint
|A79014-001||Omnetics connector - 16 channel, 18 pin, 0.025" pitch, 6 guide posts, two rows||IP-24-014||CP-24-014-SC||CP-24-014-00||Footprint
|A79022-001||Omnetics connector - 32 channel, 36 pin, 0.025" pitch, 4 guide posts||IP-40-022||CP-40-022-SC||CP-40-022-00||Footprint
Multi Housing Pedestal (including six skull screws)
|Connector Type||Description||Two connectors
|A79014-001||Omnetics connector - 16 channel, 18 pin, 0.025" pitch, 6 guide posts, two rows||CP2-20-022-SC||CP3-20-022-SC||CP4-20-022-SC||Footprint
|A79022-001||Omnetics connector - 32 channel, 36 pin, 0.025" pitch, 4 guide posts||CP2-40-022-SC||CP3-40-022-SC||CP4-40-022-SC||Footprint
Multi Housing Pedestal (Pedestal only, no screws included)
|Connector Type||Description||Two connectors
|A79014-001||Omnetics connector - 16 channel, 18 pin, 0.025" pitch, 6 guide posts, two rows||CP2-20-022-00||CP3-20-022-00||CP4-20-022-00||Footprint
|A79022-001||Omnetics connector - 32 channel, 36 pin, 0.025" pitch, 4 guide posts||CP2-40-022-00||CP3-40-022-00||CP4-40-022-00||Footprint
For over 50 years, Neuroscientists have routinely used metal microelectrodes inserted into the cortex and spinal cord to record and electrically stimulate neural elements. During this time, many electrode designs, ranging from single or bundled micro-wires to sophisticated silicon probes, have seen various successes in acute and chronic applications. For acute experiments, many neuroscientists typically fabricate bundles of micro-wires and insert them into the cortex using micro-drives.
As neuroscience research evolves to the study of large populations of cells in chronic rather than acute experiments, more sophisticated technologies must be employed to provide multi-electrode systems that can satisfy a diverse scope of experimental paradigms. Chronic experiments, which are conducted over months or even years, will require the use of intracortical microelectrodes for reliable neural interfaces for both stimulation and recording paradigms.
The need for arrays to have flexible design characteristics will be necessary to accommodate the varied experimental paradigms and animal models used among neuroscience researchers. Multi-electrode arrays that may have regular or irregular electrode-to-electrode geometric spacing, with multiple electrode depths that can stimulate or record from neurons without causing tissue damage or deterioration of the electrodes, are becoming essential tools. Even in the peripheral nervous system, emerging studies are investigating arrays of electrodes inserted into the spinal cord or nerve branches, with irregular electrode spacing, depth, and metal type as a means of providing a more sophisticated artificial neural interface.
Current research on neural prosthesis applications, including cochlear nucleus stimulation for an auditory prosthesis, cortical stimulation for a visual prosthesis, and cortical recording for brain-machine interfaces, all require use of electrode arrays maintained in a stable mechanical position relative to the associated neuronal structures.
We have commercialized this innovated Floating Microelectrode Array FMA whose design permits the mixing of electrode types, impedance values, irregular electrode spacing, arbitrary electrode lengths, and electrode metals such as Platinum-Iridium and activated-iridium-oxide, within the same microelectrode array.
There are many investigative paradigms that require electrodes contained within a single array to have a range of tips exposures, as often characterized by their impedance, or a variety of electrode shaft lengths. Sometimes recordings are performed in a differential mode, requiring a reference electrode, which typically has an impedance value that is required to be an order of magnitude less than the recording electrodes.
“Ground” or “common” electrodes are also required to be included in both recording and stimulation multi-electrode arrays. Also, it is often desirable to implant an array along a sulcus, where some of the electrodes need to be much longer along the sulcus and shorter away from the sulcus.
Our arrays are fabricated from biocompatible materials: alumina ceramic, Parylene-C, noble metals (gold, and platinum/iridium 70/30% or pure iridium), and medical implant grade silicone elastomers. Our FMAs implanted into animals have exhibited single unit activities for periods of over to 3.5 years. Moreover, researchers could record single unit activity from the same neuron for 1 month because of the floating nature of our FMAs.
Our FMA design incorporates solid core conductors instead of silicone technology for several reasons. First, as a result of our initial research with the Visual Prosthesis Program at the Illinois Institute of Technology, (directed by Dr. Phil Troyk), an electrode design was required that could withstand indefinite stimulation without compromising the metal conductor or the integrity of the insulation interface. To date, metalized silicone probes have not demonstrated sufficiently robust behavior to warrant long-term stimulation. Secondly, our work with Dr. Richard Andersen’s laboratory at Cal Tech required floating microelectrode array designs that would accommodate electrode lengths up to 8 mm.
Researchers there also expressed the desire to have electrodes with different lengths within the same array. We have worked with these groups and others to develop a very flexible array design that is also very affordable for most laboratories.