Abstract
The acquisition of high-fidelity, long-term neural recordings in vivo is critically important to advance neuroscience and brain–machine interfaces. For decades, rigid materials such as metal microwires and micromachined silicon shanks were used as invasive electrophysiological interfaces to neurons, providing either single or multiple electrode recording sites. Extensive research has revealed that such rigid interfaces suffer from gradual recording quality degradation, in part stemming from tissue damage and the ensuing immune response arising from mechanical mismatch between the probe and brain. The development of “soft” neural probes constructed from polymer shanks has been enabled by advancements in microfabrication; this alternative has the potential to mitigate mismatch-related side effects and thus improve the quality of recordings. This review examines soft neural probe materials and their associated microfabrication techniques, the resulting soft neural probes, and their implementation including custom implantation and electrical packaging strategies. The use of soft materials necessitates careful consideration of surgical placement, often requiring the use of additional surgical shuttles or biodegradable coatings that impart temporary stiffness. Investigation of surgical implantation mechanics and histological evidence to support the use of soft probes will be presented. The review concludes with a critical discussion of the remaining technical challenges and future outlook.
Highlights
As neuroscience research evolves, and as more questions about the complexity and functions of the brain arise, so too does the need for more advanced experimental tools
Microfabrication of microelectromechanical system (MEMS) devices is accomplished layer-by-layer in processing steps that involve a combination of deposition, lithographic masking, etching, and cleaning [31]
Seems promising in acute in vivo studies, long-term studies have yet to be reported [2]. Another new material used for neural probes is liquid crystal polymer (LCP), a semi-crystalline aromatic polyester, which one group fabricated using laser micromachining and thermal bonding [56]
Summary
As more questions about the complexity and functions of the brain arise, so too does the need for more advanced experimental tools. For a detailed review of the current state of the field of penetrating intracortical for the patterning of multiple electrodes along the length of the probe with creative designs and electrodes, including biological and non-biological failure modes and strategies towards improving architectures. While there has been a tremendous amount electrodes, including biological and non-biological failure modes and strategies towards improving of literature exploring the successes of silicon probes to achieve high-quality neural recordings, one device performance over time, see these reviews: [2,3]. A retrospective of 78 intracortical, Utah damage and non-biological (e.g.,implanted connectorinorrhesus electrode failure) mechanisms, including mechanical damage to Arrays chronically monkeys found the average recording lifetime to be to or chemical corrosion of electrodes and traces, degradation of passivation layers and12insulating or chemical corrosion of electrodes and traces, degradation of passivation layers and insulating coatings, a longest successful recording of 5.75 years [4].
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