Every moment, our brain processes a lot of data to understand the outside world. Thus, by mimicking the way the human brain solves everyday problems, neuromorphic systems have enormous potential to revolutionize big data analysis and pattern recognition problems, which are a struggle for current digital technologies. But in order for artificial systems to be more cerebral, they must reproduce as nerve cells communicate at their terminals, called synapses.
In a study published in the September issue of the Journal for the American Chemical Society, researchers at the University of Texas at A&M have described new material that captures the pattern of electrical activity at the synapse. Just as a nerve cell produces a pulse of oscillating current depending on the history of electrical activity at its synapse, the researchers said their material oscillates from metal to insulator at a transitional temperature decided by the thermal history of the device.
Materials are generally classified into metals or insulators depending on whether they conduct heat and electricity. But some materials, such as vanadium dioxide, live twice as long. At certain temperatures, vanadium dioxide acts as an insulator, resisting the flow of heat and electrical currents. But heated to 67 degrees Celsius, vanadium dioxide undergoes a chameleon-like change in its internal properties, transforming into a metal.
These back and forth temperature oscillations make vanadium dioxide an ideal candidate for brain-inspired electronic systems, as neurons also produce an oscillating current, called an action potential.
But neurons also join their contributions at their synapse. This integration increases the tension of the neuron membrane continuously, bringing it closer to a threshold value. When this threshold is crossed, neurons fire an action potential.
“A neuron can remember what voltage its membrane sits in and depending on where its membrane voltage is relative to the threshold, the neuron will either ignite or remain dormant,” said Dr. Sarbajit Banerjee, a professor in the Department of Materials Science and Engineering and the Chemistry Department, and one of the study’s senior authors. “We wanted to improve the property of vanadium dioxide so that it retains some memory of how close it is to the transitional temperature so that we can mimic what happens at the synapse of biological neurons.”
The transition temperatures for a given material are generally fixed unless a contaminant called dopant is added. Although dopant can move the transition temperature depending on its type and concentration within vanadium dioxide, Banerjee and his team’s goal was to perform a means to set the transition temperature up or down in a way that reflects not only the dopant’s concentration but also the time has passed since it was restarted. This flexibility, they found, was possible only when they used the drill.
When the researchers added boron to vanadium dioxide, the material still transitioned from insulator to metal, but the transition temperature now depended on how long it remained in a new metastable state created by boron.
“Biological neurons remember their membrane tension; similarly, boron-chopped vanadium dioxide remembers its thermal history, or formally speaking, how long it has been in a metastable state,” said Dr. Diane Sellers, one of the study’s primary authors and a former researcher in Banerjee’s laboratory. “This memory determines the transition temperature by which the device moves to oscillate from metal to insulator.”
While their system is an initial step to mimic biological synapse, experiments are currently underway to introduce more dynamics into the behavior of the material by controlling the kinetics of the loose process of vanadium dioxide, said Dr. Patrick Shamberger, a professor in the field of material science and 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 the current research by exploring the atomic and electronic structures of other more complex vanadium oxide compounds. In addition, the collaborative team will also explore 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 grids and other host atoms,” said Dr. Raymundo Arróyave, a professor in the materials science department and author of the study. “This understanding can provide us with several tools to further customize the properties of these types of neuromorphic materials for a variety of applications.”
Erick J. Braham of the Department of Chemistry is co-lead author of this study. Other contributors to this research include Baiyu Zhang, Drs. Timothy D. Brown and Heidi Clarke from the materials science department; Ruben Villarreal of the Department of Mechanical Engineering J. Mike Walker ’66; Abhishek Parija, Theodore EG Relief and Dr. Luis R. De Jesus of the Chemistry Department; Dr. Lucia Zuin of the University of Saskatchewan, Canada; and Dr. David Prendergast of the 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 Mobile Doping Diffusion in VO2, Journal for the American Chemical Society (2020). DOI: 10.1021 / jacs.0c07152
Provided by Texas University Engineering A&M
Quote: Chameleon material punctured with boron closer to imitation brain cells (2020, 15 December) taken 15 December 2020 from https://phys.org/news/2020-12-chameleon-like-material-spiked-boron-closer. html
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