Being able to 'remember' the entire history of previous external stimuli like the brain (Image source: POWERlab/2022 EPFL)
Researchers at the Swiss Federal Institute of Technology in Lausanne (EPFL) have found that vanadium dioxide (VO2) is a compound used in electronic products that can "remember" the entire history of external stimuli in the past. This is the first material identified as possessing this characteristic, although there may be other materials as well.
MOHAMMAD Samizadeh Nikoo is a PhD student at the EPFL Power and Wide Bandgap Electronics Research Laboratory (POWERlab), who accidentally discovered this discovery while studying VO2 phase transition. He and his colleagues reported their findings in a paper published in Nature Electronics.
When relaxed at room temperature, VO2 is insulating, but it undergoes a steep transition from insulator to metal at 68 ° C, causing a change in its lattice structure. However, this state will not last long: "The material immediately returns to an insulating state after removing the excitation," Nikoo said.
In his paper, Nikoo began exploring how long it takes for VO2 to transition from one state to another. But his research led him down a different path - after conducting hundreds of measurements, he observed memory effects in material structures.
In his experiment, Nikoo applied current to the sample of VO2. The current passes through the material and moves along a path until it exits from the other side, "he explained.
When the current heats the sample, it causes a change in the state of VO2. Then, once the current passes through, the material will return to its initial state. But when Nikoo applied a second current pulse to the material, he found that the time required to change the state was directly related to the history of the material.
VO2 seems to 'remember' the transition from the first stage and predict the transition to the next stage, "said Elison Matioli, head of POWERlab. We didn't expect to see this memory effect, which is not related to the electronic state but to the physical structure of the material. This is a novel discovery: no other material behaves in this way.
Researchers continue to discover that VO2 can remember its most recent external stimuli for up to three hours. The memory effect may actually last for a few days, but we currently do not have the necessary instruments to measure it, "Matioli said.
The findings of the research team are important because the memory effect they observed is an inherent property of the material itself. Engineers rely on memory to perform various calculations, and there is a high demand for materials to enhance the computing process by providing greater capacity, speed, and miniaturization. Check all three boxes for VO2. More importantly, its continuous structural memory distinguishes it from traditional materials that store data as binary information dependent on electronic state manipulation.
Researchers conducted extensive measurements to arrive at their findings. They also confirmed their results by applying the new method to different materials in other laboratories around the world. This discovery effectively replicates what happens in the brain, as VO2 switches can function like neurons.
