Tag Archives: Wentao Xu

Artificial synapse rivals biological synapse in energy consumption

How can we make computers be like biological brains which do so much work and use so little power? It’s a question scientists from many countries are trying to answer and it seems South Korean scientists are proposing an answer. From a June 20, 2016 news item on Nanowerk,

News) Creation of an artificial intelligence system that fully emulates the functions of a human brain has long been a dream of scientists. A brain has many superior functions as compared with super computers, even though it has light weight, small volume, and consumes extremely low energy. This is required to construct an artificial neural network, in which a huge amount (1014)) of synapses is needed.

Most recently, great efforts have been made to realize synaptic functions in single electronic devices, such as using resistive random access memory (RRAM), phase change memory (PCM), conductive bridges, and synaptic transistors. Artificial synapses based on highly aligned nanostructures are still desired for the construction of a highly-integrated artificial neural network.

Prof. Tae-Woo Lee, research professor Wentao Xu, and Dr. Sung-Yong Min with the Dept. of Materials Science and Engineering at POSTECH [Pohang University of Science & Technology, South Korea] have succeeded in fabricating an organic nanofiber (ONF) electronic device that emulates not only the important working principles and energy consumption of biological synapses but also the morphology. …

A June 20, 2016 Pohang University of Science & Technology (POSTECH) news release on EurekAlert, which originated the news item, describes the work in more detail,

The morphology of ONFs is very similar to that of nerve fibers, which form crisscrossing grids to enable the high memory density of a human brain. Especially, based on the e-Nanowire printing technique, highly-aligned ONFs can be massively produced with precise control over alignment and dimension. This morphology potentially enables the future construction of high-density memory of a neuromorphic system.

Important working principles of a biological synapse have been emulated, such as paired-pulse facilitation (PPF), short-term plasticity (STP), long-term plasticity (LTP), spike-timing dependent plasticity (STDP), and spike-rate dependent plasticity (SRDP). Most amazingly, energy consumption of the device can be reduced to a femtojoule level per synaptic event, which is a value magnitudes lower than previous reports. It rivals that of a biological synapse. In addition, the organic artificial synapse devices not only provide a new research direction in neuromorphic electronics but even open a new era of organic electronics.

This technology will lead to the leap of brain-inspired electronics in both memory density and energy consumption aspects. The artificial synapse developed by Prof. Lee’s research team will provide important potential applications to neuromorphic computing systems and artificial intelligence systems for autonomous cars (or self-driving cars), analysis of big data, cognitive systems, robot control, medical diagnosis, stock trading analysis, remote sensing, and other smart human-interactive systems and machines in the future.

Here’s a link to and a citation for the paper,

Organic core-sheath nanowire artificial synapses with femtojoule energy consumption by Wentao Xu, Sung-Yong Min, Hyunsang Hwang, and Tae-Woo Lee. Science Advances  17 Jun 2016: Vol. 2, no. 6, e1501326 DOI: 10.1126/sciadv.1501326

This paper is open access.

Korean researchers fabricate cross-shaped memristors

I’ve been a bit late getting this Korean research concerning memristors into a posting. A Jan. 30, 2016 news item on Nanotechnology Now announces a new means of fabricating memristors,

Along with the fast development of modern information technology, charge-based memories, such as DRAM and flash memory, are being aggressively scaled down to meet the current trend of small size devices. A memory device with high density, faster speed, and low power consumption is desired to satisfy Moore’s law in the next few decades. Among the candidates of next-generation memory devices, cross-bar-shaped non-volatile resistive memory (memristor) is one of the most attractive solutions for its non-volatility, faster access speed, ultra-high density and easier fabrication process.

Conventional memristors are usually fabricated through conventional optical, imprint, and e-beam lithographic approaches. However, to meet Moore’s law, the assembly of memristors comprised of 1-dimensional (1D) nanowires must be demonstrated to achieve cell dimensions beyond limit of state-of-art lithographic techniques, thus allowing one to fully exploit the scaling potential of high density memory array.

Prof. Tae-Woo Lee (Dept. of Materials Science and Engineering) and his research team have developed a rapid printing technology for high density and scalable memristor array composed of cross-bar-shaped metal nanowires. The research team, which consists of Prof. Tae-Woo Lee, research professor Wentao Xu, and doctoral student Yeongjun Lee at POSTECH [Pohang University of Science and Technology], Korea, published their findings in Advanced Materials.

A Jan. 28, 2016 POSTECH news release, which originated the news item, expands on the theme,

They applied an emerging technique, electrohydrohynamic nanowire printing (e-NW printing), which directly prints highly-aligned nanowire array on a large scale into the fabrication of microminiature memristors, with cross-bar-shaped conductive Cu nanowires jointed with a nanometer-scale CuxO layer. The metal-oxide-metal structure resistive memory device exhibited excellent electrical performance with reproducible resistive switching behavior.

This simple and fast fabrication process avoids conventional vacuum techniques to significantly reduce the industrial-production cost and time. This method paved the way to the future down-scaling of electronic circuits, since 1D conductors represent a logical way to extreme scaling of data processing devices in the single-digit nanometer scale.

They also succeeded in printing memristor array with various shapes, such as parallel lines with adjustable pitch, grids, and waves which can offer a future stretchable memory for integration into textile to serve as a basic building block for smart fabrics and wearable electronics.

“This technology reduces lead time and cost remarkably compared with existing manufacturing methods of cross-bar-shaped nanowire memory and simplifies its method of construction,” said Prof. Lee. “In particular, this technology will be used as a source technology to realize smart fabric, wearable computers, and textile electronic devices.”

Here’s a link to and a citation for the paper,

[Nanowires:] Simple, Inexpensive, and Rapid Approach to Fabricate Cross-Shaped Memristors Using an Inorganic-Nanowire-Digital-Alignment Technique and a One-Step Reduction Process by Wentao Xu, Yeongjun Lee, Sung-Yong Min, Cheolmin Park, andTae-Woo Lee. Advanced Materials Volume 28, Issue 3 January 20, 2016 Page 591  DOI: 10.1002/adma.201503153 Article first published online: 20 NOV 2015

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.