{"id":2490472,"date":"2020-12-21T12:18:04","date_gmt":"2020-12-21T17:18:04","guid":{"rendered":"https:\/\/www.futurity.org\/?p=2490472"},"modified":"2020-12-21T12:19:23","modified_gmt":"2020-12-21T17:19:23","slug":"synapses-vanadium-dioxide-boron-neuromorphic-computing-2490472-2","status":"publish","type":"post","link":"https:\/\/www.futurity.org\/synapses-vanadium-dioxide-boron-neuromorphic-computing-2490472-2\/","title":{"rendered":"Tweak gets chameleon material to mimic brain cells"},"content":{"rendered":"
Adding small quantities of the element boron to vanadium dioxide makes the material function like a synapse, researchers report.<\/p>\n
Each waking moment, our brain processes a massive amount of data to make sense of the outside world. Thus, by imitating the way the human brain solves everyday problems, neuromorphic<\/a> systems have tremendous potential to revolutionize big data analysis and pattern recognition problems that are a struggle for current digital technologies.<\/p>\n For artificial systems to be more brain-like, however, they need to replicate how nerve cells communicate at their terminals, called the synapses.<\/p>\n In the study in Journal of the American Chemical Society<\/em><\/a>, researchers described a new material that captures the pattern of electrical activity at the synapse.<\/p>\n Much like how a nerve cell produces a pulse of oscillating current depending on the history of electrical activity at its synapse, the researchers say their material oscillates from metal to insulator at a transition temperature decided by the device’s thermal history.<\/p>\n Materials are generally classified into metals or insulators depending on whether they conduct heat and electricity. But some materials, like vanadium dioxide, lead a double life. At certain temperatures, vanadium dioxide acts like an insulator, resisting the flow of heat and electric currents. But when heated to 67 degrees Celsius (152.6 degrees Fahrenheit), vanadium dioxide undergoes a chameleon-like change in its internal properties, converting to a metal.<\/p>\n These back-and-forth oscillations due to temperature make vanadium dioxide an ideal candidate for brain-inspired electronic systems since neurons also produce an oscillatory current, called an action potential.<\/p>\n But neurons also pool their inputs at their synapse. This integration increases the voltage of the neuron’s membrane steadily, bringing it closer to a threshold value. When this threshold is crossed, neurons fire an action potential.<\/p>\n “A neuron can remember what voltage its membrane is sitting at and depending on where its membrane voltage is with respect to the threshold, the neuron will either fire or stay dormant,” says Sarbajit Banerjee, a professor in the materials science and engineering department and the chemistry department at Texas A&M University, and one of the senior authors of the study.<\/p>\n “We wanted to tweak the property of vanadium dioxide so that it retains some memory of how close it is to the transition temperature so that we can begin to mimic what is happening at the synapse of biological neurons.”<\/p>\n The transition temperatures for a given material are generally fixed unless an impurity, called a dopant, is added. Although a dopant can move the transition temperature depending on its type and concentration within vanadium dioxide, Banerjee and his team’s objective was to imbue a means of tuning the transition temperature up or down in a way reflecting not just the concentration of the dopant but also the time elapsed since it had been reset. This flexibility, they found, was only possible when they used the boron.<\/p>\n When the researchers added boron<\/a> to vanadium dioxide, the material still transitioned 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.<\/p>\n