A new research team has developed a new type of artificial synapse based on two-dimensional materials for highly scalable brain-inspired computing. The research team was led by Assistant Professor Desmond Loke from the Singapore University of Technology and Design.
Brain-inspired computing mimics the human brain functions. This has drawn significant scientific attention because of its uses in artificial intelligence functions and low energy consumption. For brain-inspired computing to work, synapses remembering the connections between two neurons are necessary, like human brains.
In developing brains, synapses are grouped into functional synapses and silent synapses. The synapses are active in functional synapses. In silent synapses, the synapses are inactive under normal conditions. Silent synapses can help to optimize the connections between neurons when activated. Artificial synapses built on digital circuits typically occupy large spaces. There are usually limitations in terms of hardware efficiency and costs. Human brain contains about a hundred trillion synapses. So, it is necessary to improve the hardware cost in order to apply it to smart portable devices and internet-of things.
The SUTD research team has mimicked behaviors of functional and silent synapses using 2D materials. This artificial synapse demonstrates that it can be implemented with the same device that functions as both functional and silent synapses for the first time.
Scientists mentioned that this work can dramatically reduce the hardware costs. As it will replace functional and silent synapses that were based on complex digital circuits with a single device.
In neurobiology, silent synapses would not generate excitatory behavior when presynaptic neurons receive continuous stimuli. As they contain N-methyl-D-aspartate receptors and but they lack the alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic-acid receptors. But silent synapses can be activated to become functional synapses. It will also respond to stimulations upon the insertion of AMPA receptors after consecutive stimulations.
The researchers have been inspired by the biological mechanism for silent synapse activation through the insertion of AMPA receptors. Transformations from silent synapses to functional synapses in devices can be achieved by introducing sulfur anions in 2D indium selenide material systems. The sulfur anions in indium selenide can migrate under an electric field and show functional synaptic plasticity. The new device is based on a fully sulfurized type of system which shows obvious memristive behavior at room temperature. It can be used to implement functional synapses. silent synapses activation can be demonstrated using a partially sulfurized type of system by modifying the temperature.
This research paper has been published in ACS Applied Materials & Interfaces.