Science Concentrates NANOMATERIALS
Electronic device mimics neurons Phase-change material could help electronics compute like neurons
Fire!
Although processors have gotten smaller and faster over time, few Electrical pulses convert a doped chalcogenide computers can compete with from an amorphous phase (pink) into a crystalline the speed and computing power one (blue). Once a certain amount has been conof the human brain. And none verted, the conductance of the material suddenly comes close to the organ’s energy jumps, mimicking the firing of a neuron. efficiency. So some engineers Conductance want to develop electronics that mimic how the brain computes to build more powerful and efficient devices. A team at IBM Research, Zurich, now reports that nanosized devices made from phase-change materials can mimic how neurons fire to perform certain calculations (Nat. Nanotechnol. 2016, DOI: 10.1038/ nnano.2016.70). This report “shows quite concretely that we can make simple but effective hardware mimics of neurons, which could be made really small and therefore have low operating powers,” says C. David Number of pulses Wright, an electrical engineer at the University of Exeter who wrote Source: Adapted from Nat. Nanotechnol. a commentary accompanying the new article. slowly convert the material from amorThe IBM team’s device imitates how an phous to crystalline, which, in turn, changes individual neuron integrates incoming sigits conductance. At a certain level of phase nals from other neurons to determine when change, the material’s conductance suddenit should fire. These input signals change ly jumps, and the device fires like a neuron. the electrical potential across the neuron’s The IBM team tested a mushroom-shaped membrane—some increase it, others dedevice consisting of a 100-nm-thick layer of crease it. Once that potential passes a certhe chalcogenide sandwiched between two tain threshold, the neuron fires. electrodes. In one demonstration, they used Previously, engineers have mimicked the neuronlike device to detect correlations this process using combinations of capacin 1,000 streams of binary data. Such a calitors and silicon transistors, which can be culation could spot trends in social media complex and difficult to scale down, Wright chatter or even in stock market transactions, explains in his commentary. Wright says. In the new work, IBM’s Evangelos He also points out that the devices fire Eleftheriou and colleagues demonstrate faster than actual neurons, on a nanoseca potentially simpler system that uses a ond timescale compared with a millisecond phase-change material to play the part of a one. The neuron mimics, Wright says, are neuron’s membrane potential. The doped another step toward hardware that can chalcogenide Ge2Sb2Te5, which has been process information as the brain does but tested in conventional memory devices, at speeds orders of magnitudes faster than can exist in two phases: a glassy amorphous the organ. “That could do some remarkable state and a crystalline one. Electrical pulses things.”—MICHAEL TORRICE
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C&EN | CEN.ACS.ORG | MAY 23, 2016
