Abstract
Neural probes for intracortical neuromodulation in the brain have advanced with the developments in micro- and nanofabrication technologies. Most of these technologies for the intracortical stimulation have relied on the direct electrical stimulation via electrodes or arrays of electrodes. Generating electric fields using time-varying magnetic fields is a more recent neuromodulation technique that has proven to be more specifically effective for the intracortical stimulation. Additionally, current-actuated coils require no conductive contact with tissues and enable precise tailoring of magnetic fields, which are unaffected by the non-magnetic nature of the biological tissue and encapsulation layers. The material and design parameter space for such micro-coil fabrication can be optimized and tailored to deliver the ideal performance depending on the parameters needed for operation. In this work, we review the key requirements for implantable microcoils including the probe structure and material properties and discuss their characteristics and related challenges for the applications in intracortical neuromodulation.
Highlights
Intracortical neuromodulation utilizing implantable neural probes has developed into a de facto standard in a number of clinical applications to treat a wide range of neurological (e.g., Parkinson’s disease1) and psychological health issues
We have demonstrated several novel results using a novel form of the intracortical stimulation, namely, magnetic stimulation via the use of microcoils
We demonstrated the effective use of a new generation of advanced microcoils that we developed at Palo Alto research center (PARC) to customize and individualize design features resulting in controlled influence over both the selectivity and strength of the neuromodulation7 to induce a desired response in vitro
Summary
Scitation.org/journal/apm insight into the design parameter space including spatial resolution, temporal resolution, ex vivo stability, and selectivity with which signals can be delivered, with the aim of assisting in the development of the next-generation cortical prostheses. We discuss the challenges and advantages that the micro-coil technology provides vis-à-vis the material properties and design properties of the microcoils themselves and offer design suggestions for intracortical neural stimulation devices. A comparison of the performance with current state-of-the-art electrode technologies for intracortical stimulation is provided, and the advantages of our technology are discussed in detail. We explore optimizing the mechanical properties of the device to enable chronic implantation while reducing tissue damage and scarring, as discussed in the section on mechanical properties (Sec. II B). An advantage of such contactless microcoils is that they allow the use of conventionally toxic metals with superior electrical properties to be encapsulated and isolated from tissue. After the material properties have been decided, there is still a large parameter space of micro-coil design (Sec. III) that can be optimized for the end application. The microcoil technology presented here has several distinct advantages over the conventional electrode technology for the use in intracortical stimulation and can provide a significant advantage for future advanced cortical prostheses
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