What is Microelectrode Array?

A device consisting of multiple microscale electrodes arranged in a defined geometry for simultaneously recording from or stimulating many sites in neural tissue.

What category does Microelectrode Array belong to in BCI?

Microelectrode Array is a Devices concept in brain-computer interface science.

Microelectrode Array — BCI Glossary

A microelectrode array (MEA) is a multi-electrode device with microscale recording or stimulation sites, designed to interface with neural tissue at the cellular level. MEAs are the core hardware component of intracortical BCIs, enabling simultaneous recording from dozens to thousands of neurons across a region of cortex. The term encompasses both penetrating arrays (electrodes that enter brain tissue) and surface arrays (electrodes that sit on the cortical surface at micro-scale resolution).

Types of Microelectrode Arrays

Penetrating Arrays

Utah Array: 96 silicon shanks in a 10x10 grid (minus corners), 1-1.5 mm long. The gold standard for human intracortical BCI research.
Michigan Probe: Silicon-based probes with multiple electrode sites along a single shank, enabling recording at different cortical depths. Developed at the University of Michigan.
Neuralink N1 threads: 64 flexible polymer threads, each carrying 16 electrode sites, totaling 1,024 channels. Inserted by a robotic system.
Neuropixels: High-density silicon probes with 384-960 recording sites along a single shank, primarily used in animal neuroscience research.

Surface Arrays (micro-ECoG)

Precision Layer 7: 1,024-channel thin-film ECoG array, 20 micrometers thick, conforming to the cortical surface.
Research micro-ECoG grids: Sub-millimeter electrode spacing for high-resolution cortical surface mapping.

Design Parameters

Key design parameters for MEAs include electrode count (determining spatial coverage), electrode pitch (spacing between sites), shank length (determining recording depth), electrode material (platinum, iridium oxide, PEDOT:PSS), substrate material (silicon, polyimide, parylene), and impedance (affecting noise and signal quality).

Manufacturing

MEA fabrication uses semiconductor microfabrication techniques — photolithography, thin-film deposition, reactive ion etching — adapted from the integrated circuit industry. The Utah Array is fabricated from a single block of silicon using a dicing saw and wet etching. Flexible polymer arrays (Neuralink, Precision) use thin-film processes on polyimide or parylene substrates.

Challenges

The primary challenges for chronic MEAs are biocompatibility (minimizing foreign body response), mechanical compliance (matching the softness of brain tissue), connector reliability, and scaling to higher channel counts while maintaining implant size constraints. The transition from rigid silicon to flexible polymer substrates represents the major current trend in MEA development.