The full Neuralink paper describing how their multi-thousand channel brain interface system will be built and implanted is here. It is called “An integrated brain-machine interface platform with thousands of channels”.
Neuralink believes the key to high fidelity brain interfaces is to precisely reading the electrical spiking of the brain.
They call this roughly ten thousand probe sensors as the N1 system. Clearly the N2 system would be at least 10 times or 100 times higher in channel count. They want to reach the entire motor cortex and decode all signals. The current system would maximally scale to a few million probes and connections but they will have to get much smaller for billions of connections and sensors.
Neuralink wants to implant the system into a human by the end of 2020. Elon Musk described a 2-millimeter keyhole incision that would be created to implant the devices in under one hour. The hole would be glued shut with surgical glue. The needle of the surgery robot currently has a 24-micron needle.
The surgery needle is milled from 40 μm diameter tungsten-rhenium wire-stock electrochemically etched to 24 μm diameter along the inserted length. The tip of the needle is designed both to hook onto insertion loops—for transporting and inserting individual threads—and to penetrate the meninges and brain tissue. The needle is driven by a linear motor allowing variable insertion speeds and rapid retraction acceleration (up to 30,000 mm s−2) to encourage separation of the probe from the needle. The pincher is a 50 μm tungsten wire bent at the tip and driven both axially and rotationally. It serves as support for probes during transport and as a guide to ensure that threads are inserted along the needle path.
Neuralink (Elon Musk’s company) have built arrays of small and flexible electrode “threads”, with as many as 3,072 electrodes per array distributed across 96 threads. They have also built a neurosurgical robotcapable of inserting six threads (192 electrodes) per minute. Each thread can be individually inserted into the brain with micron precision for avoidance of surface vasculature and targeting specific brain regions.
Other researchers have demonstrated human neuroprosthetic control of computer cursors, robotic limbs, and speech synthesizers using no more than 256 electrodes.
Neuralink will have a wireless interface to the chip.
The electrode array is packaged into a small implantable device that contains custom chips for low-power on-board amplification and digitization: the package for 3,072 channels occupies less than (23 × 18.5 × 2) cubic millimeter. A single USB-C cable provides full-bandwidth data streaming from the device, recording from all channels simultaneously. This system has achieved a spiking yield of up to 85.5 % in chronically implanted electrodes. Neuralink’s approach to BMI has unprecedented packaging density and scalability in a clinically relevant package.
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