From - Knowable maagazine ,
By - Kurt Kleiner,
Researchers are developing novel computers made from soft, organic materials (right) that can operate like biological nerve cells (left). These new materials may someday be able to interact with real nerve cells, opening the door to better control of prosthetic limbs, among other uses.- CREDIT: W. XU ET AL / SCIENCE ADVANCES 2016
The human brain is an amazing computing machine. Weighing only three pounds or so, it can process information a thousand times faster than the fastest supercomputer, store a thousand times more information than a powerful laptop, and do it all using no more energy than a 20-watt lightbulb.
Researchers are trying to replicate this success using soft, flexible organic materials that can operate like biological neurons and someday might even be able to interconnect with them. Eventually, soft “neuromorphic” computer chips could be implanted directly into the brain, allowing people to control an artificial arm or a computer monitor simply by thinking about it.
Like real neurons — but unlike conventional computer chips — these new devices can send and receive both chemical and electrical signals. “Your brain works with chemicals, with neurotransmitters like dopamine and serotonin. Our materials are able to interact electrochemically with them,” says Alberto Salleo, a materials scientist at Stanford University who wrote about the potential for organic neuromorphic devices in the 2021 Annual Review of Materials Research.
Salleo and other researchers have created electronic devices using these soft organic materials that can act like transistors (which amplify and switch electrical signals) and memory cells (which store information) and other basic electronic components.
The work grows out of an increasing interest in neuromorphic computer circuits that mimic how human neural connections, or synapses, work. These circuits, whether made of silicon, metal or organic materials, work less like those in digital computers and more like the networks of neurons in the human brain.
Conventional digital computers work one step at a time, and their architecture creates a fundamental division between calculation and memory. This division means that ones and zeroes must be shuttled back and forth between locations on the computer processor, creating a bottleneck for speed and energy use.
The brain does things differently. An individual neuron receives signals from many other neurons, and all these signals together add up to affect the electrical state of the receiving neuron. In effect, each neuron serves as both a calculating device — integrating the value of all the signals it has received — and a memory device: storing the value of all of those combined signals as an infinitely variable analog value, rather than the zero-or-one of digital computers.
Researchers have developed a number of different “memristive” devices that mimic this ability. When you run electric currents through them, you change the electrical resistance. Like biological neurons, these devices calculate by adding up the values of all the currents they have been exposed to. And they remember through the resulting value their resistance takes.
A simple organic memristor, for example, might have two layers of electrically conducting materials. When a voltage is applied, electric current drives positively charged ions from one layer into the other, changing how easily the second layer will conduct electricity the next time it is exposed to an electric current. (See diagram.) “It’s a way of letting the physics do the computing,” says Matthew Marinella, a computer engineer at Arizona State University in Tempe who researches neuromorphic computing.
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