The Utah Array, a history

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The idea

Normann wanted to stimulate visual cortex to produce phosphenes for the blind and needed many electrodes penetrating a millimetre into the cortex, spaced closely. Existing microwires were placed one at a time. The array’s manufacturing insight was to make all hundred needles from one silicon block: dice a grid of deep cuts, etch the resulting columns into sharp tapered needles in acid, insulate them, and expose and metallize the tips. The process, refined by Patrick Rousche, Kelly Jones, and others through the 1990s, produced arrays whose geometry was reproducible, which made them a research tool rather than a craft object.

From cats to humans

Recording rather than stimulation turned out to be the first application. The array recorded populations of neurons in cat and monkey cortex through the 1990s, and the Utah group and others showed that its hundred channels captured enough of motor cortex to decode arm movement. BrainGate, the academic consortium led from Brown University, implanted the first array in a person with tetraplegia in 2004; he moved a cursor, opened email, and controlled a prosthetic hand. Every human intracortical BCI result for the next two decades (cursor control, robotic arms, handwriting at 90 characters per minute, speech at 60 to 80 words per minute, touch feedback through microstimulation) used Utah Arrays.

The company

Cyberkinetics licensed the technology for the first human work, then Blackrock Microsystems, founded in Salt Lake City in 2008 by Marcus Gerhardt and Florian Solzbacher (a Utah faculty member and Nanofab director), took over manufacturing. Blackrock, now Blackrock Neurotech, made the arrays and the recording systems for the entire human field, obtained the first FDA clearance for a Utah Array-based system for research use in humans, and has Breakthrough Device designation for a BCI system aimed at paralysis. The Utah Slanted Electrode Array, with graded needle lengths for peripheral nerves, is the same platform pointed at a different tissue and is the basis of Greg Clark’s and the NeuroRobotics lab’s work on restoring touch to amputees.

The regulatory path

The array reached humans through investigational device exemptions: research-use studies under IRB and FDA oversight, a handful of participants at a time, for two decades. No Utah Array system is approved as a treatment; every participant has been in a trial. Blackrock’s clearance covers the array as a research recording device. The approval of any intracortical BCI as a therapy, by anyone, has not yet happened, and its path (a pivotal trial, a PMA, a reimbursement code) is what the industry is now walking.

The limits

Ninety-six channels, when modern probes have a thousand or more. Rigid silicon, with the tissue response described in the materials explainer: recording yield declines over years. A percutaneous pedestal through the skin for the cable, which is an infection risk and the thing patients most want gone. A fixed 1.5 millimetre depth that reaches layer 5 in some cortex and not others. The array was designed in an era of hand-placed microwires and was revolutionary; the next generation (flexible threads, thin-film grids, fully wireless cans) is defined largely by trying to keep what it gave and remove what it costs.

Why it matters that it was here

Because the physical center of invasive BCI hardware is thirty minutes from campus and the people who built it are still on the faculty. Because the Nanofab that makes new electrodes trains student users. Because the history above means that a student who walks into Blackrock or Ripple with a characterized amplifier and a coated microelectrode is walking into a company that knows exactly what those are worth. The Utah map is the rest of the argument.