WIMAGINE: Wireless 64-Channel ECoG Recording Implant for Long Term Clinical Applications

Abstract

A wireless 64-channel ElectroCorticoGram (ECoG) recording implant named WIMAGINE has been designed for various clinical applications. The device is aimed at interfacing a cortical electrode array to an external computer for neural recording and control applications. This active implantable medical device is able to record neural activity on 64 electrodes with selectable gain and sampling frequency, with less than 1 μV(RMS) input referred noise in the [0.5 Hz - 300 Hz] band. It is powered remotely through an inductive link at 13.56 MHz which provides up to 100 mW. The digitized data is transmitted wirelessly to a custom designed base station connected to a PC. The hermetic housing and the antennae have been designed and optimized to ease the surgery. The design of this implant takes into account all the requirements of a clinical trial, in particular safety, reliability, and compliance with the regulations applicable to class III AIMD. The main features of this WIMAGINE implantable device and its architecture are presented, as well as its functional performances and long-term biocompatibility results.

Silicon-Integrated High-Density Electrocortical Interfaces

“…Some of these IMDs can be wholly placed on the cortex within a very limited geometry as shown in Fig. 2(b) In other cases, only the electrode array is placed on the cortex while the other components can be located in the empty space created by a craniotomy [122], or under the scalp with lead wires connected [123], [124]. Regardless of placement, this constrained environment poses a difficult power challenge.…”

“…For devices implanted to a depth of a few centimeters, and that are on the order of millimeter-to-centimeter in diameter, near-or mid-field electromagnetic power transfer is generally considered to be the most efficient and practical method to power such devices. Near-field power transfer, which operates at frequencies up to approximately 100 MHz for typical implants, has been extensively used for cochlear implants [135], retinal prostheses [86], [93], and various research IMD systems [122], [136]- [139], and has been investigated and characterized to maximize its usage and power transfer efficiency for implants [140]- [145].…”

“…Due to the wide availability of far-field radio products and a myriad of different infrastructures (e.g., Bluetooth Low Energy, WiFi, etc. ), farfield radios can be quickly adopted for robust operation [122]. However, even state-of-the-art low-power radios consume 9 1 nJ/b [125], [164], which is order-ofmagnitude larger than what typical ECoG recording IMDs require.…”

“…Thus far, titanium-, glass-or ceramicbased enclosures have been the primary means for hermetic sealing in long-term implants, since these hard materials have been shown to be biocompatible and impermeable to water [181]. Even though such hard enclosures are used in the majority of long-term implants [6], [111], [122], [150]- [155], [159], [183], their very large volume and weight, typically much larger than the ICs and supporting components they contain, prohibits their use in high-dimensional neural interfaces heavily constrained by anatomical space such as retinal prostheses [184] and ECoG arrays [30]. In addition, hard packaging requires intricate methods for hermetic sealing of feedthroughs to polymer insulated extensions of the implant such as electrode array cabling, limiting the density of electrode channels due to feedthrough channel spacing requirements.…”

“…One such device is the Wireless Implantable Multichannel Acquisition system for Generic Interface with NEurons (WIMAGINE), which features up to 64 channels, targeting long-term ECoG recording fully implanted in human patients [122] as shown in Fig. 7(d).…”