Abstract
We devised a scalable, modular strategy for microfabricated 3-D neural probe synthesis. We constructed a 3-D probe out of individual 2-D components (arrays of shanks bearing close-packed electrodes) using mechanical self-locking and self-aligning techniques, followed by electroless nickel plating to establish electrical contact between the individual parts. We detail the fabrication and assembly process and demonstrate different 3-D probe designs bearing thousands of electrode sites. We find typical self-alignment accuracy between shanks of <0.2° and demonstrate orthogonal electrical connections of 40 µm pitch, with thousands of connections formed electrochemically in parallel. The fabrication methods introduced allow the design of scalable, modular electrodes for high-density 3-D neural recording. The combination of scalable 3-D design and close-packed recording sites may support a variety of large-scale neural recording strategies for the mammalian brain.
Highlights
Silicon microfabricated neural probes [1,2,3,4,5,6,7,8,9,10] offer the capability of scalable neural recording in acute and chronic neuroscience experiments [8,9,10,11], since hundreds of, or more, electrode recording sites can be created on an implantable 1-D or 2-D shank using scalable microfabrication techniques
We have demonstrated fabrication and assembly technologies for 3-D probes and showed new methods to build scalable and close packed electrode recording sites, focusing on scalability of both the number of shanks as well as the number of recording sites per shank
The use of scaled 3-D probes in vivo will benefit from recent advances in surgery and experimental design (e.g., [39,54]) that will allow scaling up the number of recording sites without the constraints that chronic implant systems require
Summary
Silicon microfabricated neural probes [1,2,3,4,5,6,7,8,9,10] offer the capability of scalable neural recording in acute and chronic neuroscience experiments [8,9,10,11], since hundreds of, or more, electrode recording sites can be created on an implantable 1-D or 2-D shank using scalable microfabrication techniques. We designed, implemented and used 2-D silicon microelectrode arrays bearing close-packed recording sites, designed with small enough spacing to enable spatial oversampling of extracellular action potentials—and scalable, tetrode-style analysis to be performed on the data obtained [12] We explore another key aspect of scalability, namely how to fabricate silicon microfabricated neural probes with electrode pads distributed in 3-D, not just 2-D, patterns. Our primary focus is to explore the scalability of 3-D assembly of modular microfabricated neural probes, aiming to develop robust, powerful methods for assembling probes bearing many thousands of electrode recording sites and beyond We approach this by introducing electroless plating as a way of forming, in a simple single step, all of the electrical connections at the same time—thereby enabling a new efficient and scalable fabrication method
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