Wireless Floating Microelectrode Array (WFMA)

Type: Electrophysiology / Probes,

Keywords: Microelectrode array, Magnetic wireless transmission, Neural interface, Neural implant, BRAIN Initiative

CNS stimulation and recording through a magnetic, wireless link

The Floating Microelectrode Array allows stimulation and recording from the CNS and the periphery through a wireless link. This device is 5mm diameter and can interface to 16 electrodes without any wires or tethers. Power and communication is through a magnetic wireless link. The WFMA is being used for a clinical trial of cortical visual prosthesis, but has also been used for peripheral nerve (cuff) interface. Currently it is being deployed for neuroscience research through a joint effort by MicroProbes for Life Science and Sigenics, Inc.

* Pioneered the design and fabrication of multi-channel Wireless Floating Microelectrode Array (WFMA) devices for the purpose of stimulating the brain’s visual centers
* Developed a 16-channel wireless floating microelectrode array (WFMA) for chronic implantation
* Sophisticated neural interface that is typically best suited for chronic recording and/or stimulation in large animal cortex
* 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
* The cutting edge WFMA device currently in testing for the human ICVP project, and will be adapted in the near future to support a variety of cortical, peripheral, and spinal implants
* Multi-electrode system made from biocompatible material that is electrically and mechanically stable, and employs design features allowing flexibility in the geometric layout and length of the individual electrodes within the array
* Developed a rapid insertion system for the safe implantation of WFMA devices in neural tissue, thus eliminating the need for manual delivery. As such, the WFMA device and insertion system will serve as a platform for developing and testing a novel wireless intraspinal microstimulation (ISMS) system
* Multiple design constraints must be taken into consideration when designing and testing a wireless ISMS system. It may be desirable to approach the preclinical stage of this project in phases.

* First use within in-vivo experiments, using a rat sciatic nerve model
* To examine the ability of the devices to stimulate neural tissue, two of the WFMAs were implanted onto female Lewis rat sciatic nerves
* Implanted the FMA in rats and show that the FMA is capable of recording both spikes and local field potentials
* The insertion system was successfully used to implant WFMA devices in the primary motor and occipital cortex of multiple animal models. Histological analysis of neural tissue sections, obtained from chronic experiments, showed minimal damage to the surrounding tissue.

* Preliminary testing of the Wireless Floating Microelectrode Array (WFMA) in acute and chronic rat models
* Feasibility of using this platform technology for numerous peripheral and central nervous system applications
*Use in a variety of small animal and peripheral nerve studies
* Insertion System for Microelectrode Arrays: The system is also being considered for use in future experiments that aim to develop a wireless Intraspinal Microstimulation (ISMS) system capable of restoring motor function in individuals with complete spinal cord injury

* Rodent, Larger animals, Bird, NHP, Bat

* Low profile, small size, and great flexibility
* 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
* Capable of remarkably long periods of chronic use
* Small, low profile arrays allow many to be implanted into one animal (over 20 arrays in primate)
* Very flexible array design that is also very affordable for most laboratories
* Custom impedance in each microelectrode
* Custom length of each microelectrode of the array
* Up to 16 channels per array
* 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
* The length and area of the electrodes can be chosen to optimize the particular desired stimulator use
* Being able to observe the shape of the waveforms yields valuable insight into the behavior of the electrodes while under constantcurrent pulsing
* Wireless transmission distance of 3cm is impressive, considering the small size of, and the weak inductive coupling to, the WFMA.

* Width of the nerve was less than the span of the WFMA electrodes. This dimensional mismatch was responsible for the variations in electrode utilization
* The distance from the skin to the spinal cord is greater compared to that from the skin to the cortex, pushing the limits of wireless magnetic coupling
* Intraspinal Microstimulation: Placement of single electrodes involves hand delivery that relies on anatomical landmarks. While this technique might be effective for animal models, it is insufficient for clinical translation due to the tissue disruption associated with each electrode insertion. The WFMA might mitigate that problem
* intraspinal microstimulation: Following implantation, during physiological motion, tethered electrodes are often displaced from their initial position within the tissue, leading to an increased risk of infection, hemorrhage, and neurodegeneration
* intraspinal microstimulation: Tissue damage diminish the effectiveness of electrical stimulation over time
* The untethered WFMA may provide for greater long-term stability

* Troyk et al. 2015, In-Vivo Tests of a 16-Channel Implantable Wireless Neural Stimulator, Journal of Neural Engineering, 14: 1-4.

* https://microprobes.com/products/multichannel-arrays/fma

* https://mypages.iit.edu/~neural/

* http://mypages.iit.edu/~neural/intraspinal-microstimulation-isms/

* http://mypages.iit.edu/~neural/publications/


Philip Troyk, Professor


Illinois Institute of Tech