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Photo: Netherlands Institute for Neuroscience (NIN)
The idea of stimulating the brain via an implant to generate artificial visual percepts is not new and dates back to the 1970s.
However, existing systems are only able to generate a small number of artificial ‘pixels’ at a time.
At the NIN, researchers from a team led by Pieter Roelfsema are now using new implant production and implantation technologies, cutting-edge materials engineering, microchip fabrication, and microelectronics, to develop devices that are more stable and durable than previous implants.
The first results are very promising.
ELECTRICAL STIMULATION
When electrical stimulation is delivered to the brain via an implanted electrode, it generates the percept of a dot of light at a particular location in visual space, known as a ‘phosphene.’
The team developed high-resolution implants consisting of 1024 electrodes and implanted them in the visual cortex of two sighted monkeys.
Their goal was to create interpretable images by delivering electrical stimulation simultaneously via multiple electrodes, to generate a percept that was composed of multiple phosphenes.
“The number of electrodes that we have implanted in the visual cortex, and the number of artificial pixels that we can generate to produce high-resolution artificial images, is unprecedented,” says Roelfsema.
RECOGNIZING DOTS, LINES AND LETTERS
The monkeys first had to perform a simple behavioral task in which they made eye movements to report the location of a phosphene that was elicited during electrical stimulation via an individual electrode.
They were also tested on more complex tasks such as a direction-of-motion task, in which micro-stimulation was delivered on a sequence of electrodes, and a letter discrimination task, in which micro-stimulation was delivered on 8-15 electrodes simultaneously, creating a percept in the form of a letter.
The monkeys successfully recognised shapes and percepts, including lines, moving dots, and letters, using their artificial vision.
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KAUST researchers have developed a durable "electronic skin" that can mimic natural functions of human skin, such as sensing temperature and touch.
Credit: © 2020 KAUST
A material that mimics human skin in strength, stretchability and sensitivity could be used to collect biological data in real time.
Electronic skin, or e-skin, may play an important role in next-generation prosthetics, personalized medicine, soft robotics and artificial intelligence.
"The ideal e-skin will mimic the many natural functions of human skin, such as sensing temperature and touch, accurately and in real time," says KAUST postdoc Yichen Cai.
However, making suitably flexible electronics that can perform such delicate tasks while also enduring the bumps and scrapes of everyday life is challenging, and each material involved must be carefully engineered.
Most e-skins are made by layering an active nanomaterial (the sensor) on a stretchy surface that attaches to human skin.
However, the connection between these layers is often too weak, which reduces the durability and sensitivity of the material; alternatively, if it is too strong, flexibility becomes limited, making it more likely to crack and break the circuit.
"The landscape of skin electronics keeps shifting at a spectacular pace," says Cai. "The emergence of 2-D sensors has accelerated efforts to integrate these atomically thin, mechanically strong materials into functional, durable artificial skins."