In every waking moment, our brains process a huge amount of data to make sense of the outside world. Thus, by mimicking the way the human brain solves everyday problems, neuromorphic systems have enormous potential to revolutionize big data analytics and pattern recognition problems that are a struggle for current digital technologies. But for artificial systems to be more like the brain, they must replicate the way nerve cells communicate at their terminals, called synapses.
In a study published in the September issue of the Journal of the American Chemical Society, Texas A&M University researchers have described a new material that captures the pattern of electrical activity in the synapse. Just like the way a nerve cell produces an oscillating current pulse depending on the history of electrical activity in its synapse, the researchers said their material oscillates from metal to insulator at a transition temperature decided by the thermal history of the device.
Materials are generally classified into metals or insulators according to whether they conduct heat and electricity. But some materials, such as vanadium dioxide, lead a double life. At certain temperatures, vanadium dioxide acts as an insulator, resisting the flow of heat and electrical currents. But when heated to 67 degrees Celsius, vanadium dioxide undergoes a chameleonic change in its internal properties, converting to a metal.
These back-and-forth oscillations due to temperature make vanadium dioxide an ideal candidate for brain-inspired electronic systems as neurons also produce an oscillatory current, called an action potential.
But neurons pool their inputs in their synapse as well. This integration constantly increases the neuron’s membrane voltage, bringing it closer to a threshold value. When this threshold is exceeded, neurons activate an action potential.
“A neuron can remember what voltage its membrane is at, and depending on where its membrane voltage is relative to the threshold, the neuron will either turn on or stay dormant,” said Dr. Sarbajit Banerjee, professor at the department. of Materials Science and Engineering and the Department of Chemistry and one of the senior authors of the study. “We wanted to modify the property of vanadium dioxide so that it retains some memory of how close it is to the transition temperature so that we can start mimicking what’s happening at the synapse of biological neurons.”
The transition temperatures for a given material are generally fixed unless an impurity, called a dopant, is added. Although a dopant can shift the transition temperature depending on the type and concentration within the vanadium dioxide, the goal of Banerjee and his team was to create a means to regulate the transition temperature up or downward in a way that reflects not only the concentration of the dopant but also the time elapsed since it was restored. This flexibility, they found, was only possible when they used boron.
When the researchers added boron to vanadium dioxide, the material still switched from an insulator to a metal, but the transition temperature now depended on how long it remained in a new metastable state created by boron.
“Biological neurons have a memory of their membrane tension; similarly, boron pin vanadium dioxide has a memory of its thermal history, or formally speaking, how long it has been in a metastable state,” said Dr. Diane Sellers, one of the lead authors of the study and a former researcher in the Banerjee lab. “This memory determines the transition temperature at which the device is forced to oscillate from the metal to an insulator.”
While their system is an initial step to mimic a biological synapse, experiments are currently underway to introduce more dynamism into the behavior of the material by controlling the kinetics of the vanadium dioxide relaxation process, said Dr. Patrick Shamberger, a professor in the department of materials science and a corresponding author of the study.
In the near future, Dr. Xiaofeng Qiang, a professor in the materials science department and a Banerjee collaborator on this project, plans to expand current research by exploring the atomic and electronic structures of other more complex vanadium oxide compounds. Furthermore, the collaborative team will also investigate the possibility of creating other neuromorphic materials with alternative dopants.
“We would like to investigate whether the phenomenon we observed with vanadium dioxide applies to other host lattices and other host atoms,” said Dr. Raymundo Arróyave, professor in the materials science department and corresponding author of the study. “This insight can provide us with several tools to further optimize the properties of these types of neuromorphic materials for different applications.”
Erick J. Braham of the Department of Chemistry is a co-lead author of this study. Other contributors to this research include Baiyu Zhang, Drs. Timothy D. Brown and Heidi Clarke of the materials science department; Ruben Villarreal of the Department of Mechanical Engineering J. Mike Walker ’66; Abhishek Parija, Theodore EG Alivio and Dr. Luis R. De Jesus of the Department of Chemistry; Dr. Lucia Zuin of the University of Saskatchewan, Canada; and Dr. David Prendergast of Lawrence Berkeley National Laboratory, California.
Researchers are making progress in controlling chameleon material for next-generation computers
Diane G. Sellers et al. Atomic hourglass and thermometer based on the diffusion of a mobile dopant in VO2, Journal of the American Chemical Society (2020). DOI: 10.1021 / jacs.0c07152
Provided by Texas A&M University College of Engineering
Quote: Boron-Enriched Chameleon-Like Material Comes Close to Imitating Brain Cells (2020, Dec 15) recovered Dec 15, 2020 from https://phys.org/news/2020-12-chameleon-like-material-spiked -boron-closer .html
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