Neuromorphic computing has come to refer to a variety of brain-inspired computers, devices, and models that contrast the pervasive von Neumann computer architecture This biologically inspired approach has created highly connected synthetic neurons and synapses that can be used to model neuroscience theories as well as solve challenging machine learning problems The promise of the technology is to create a brain-like ability to learn and adapt, but the technical challenges are significant, starting with an accurate neuroscience model of how the brain works, to finding materials and engineering breakthroughs to build devices to support these models, to creating a programming framework so the systems can learn, to creating applications with brain-like capabilities In this work, we provide a comprehensive survey of the research and motivations for neuromorphic computing over its history We begin with a 35-year review of the motivations and drivers of neuromorphic computing, then look at the major research areas of the field, which we define as neuro-inspired models, algorithms and learning approaches, hardware and devices, supporting systems, and finally applications We conclude with a broad discussion on the major research topics that need to be addressed in the coming years to see the promise of neuromorphic computing fulfilled The goals of this work are to provide an exhaustive review of the research conducted in neuromorphic computing since the inception of the term, and to motivate further work by illuminating gaps in the field where new research is needed

A Survey of Neuromorphic Computing and Neural Networks in Hardware.

Fabrication of Micro/Nanoscale Motors.

The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular, the realization of large-area digital circuitry like flexible near field communication tags and analog integrated circuits such as bendable operational amplifiers is presented. The last topic of this review is devoted for emerging flexible electronic systems, from foldable displays, power transmission elements to integrated systems for large-area sensing and data storage and transmission. Finally, the conclusions are drawn and an outlook over the field with a prediction for the future is provided.

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Metal oxide semiconductor thin-film transistors for flexible electronics

Recent advances in flexible and stretchable electronics (FSE), a technology diverging from the conventional rigid silicon technology, have stimulated fundamental scientific and technological research efforts. FSE aims at enabling disruptive applications such as flexible displays, wearable sensors, printed RFID tags on packaging, electronics on skin/organs, and Internet-of-things as well as possibly reducing the cost of electronic device fabrication. Thus, the key materials components of electronics, the semiconductor, the dielectric, and the conductor as well as the passive (substrate, planarization, passivation, and encapsulation layers) must exhibit electrical performance and mechanical properties compatible with FSE components and products. In this review, we summarize and analyze recent advances in materials concepts as well as in thin-film fabrication techniques for high-k (or high-capacitance) gate dielectrics when integrated with FSE-compatible semiconductors such as organics, metal oxides, quantum...

High- k Gate Dielectrics for Emerging Flexible and Stretchable Electronics

Efficient Carbon Nanotube Photodiodes A single photon absorbed in a single-walled carbon nanotube device can generate multiple unbound particles carrying an electric charge. Gabor et al. (p. 1367) report that in such a device at low temperatures, excitation with light of increasing energy leads to well-defined stepwise increases in current. Interestingly, because of the unique band structure of carbon nanotubes, this behavior is analogous to particle-antiparticle creation commonly observed in high-energy particle physics. These observations point to the promise of investigations in other nanoscale carbon systems, such as graphene, and could lead to numerous applications, including highly sensitive photon detection and ultra-efficient photovoltaics. The decay of photoexcited electrons in a carbon nanotube device creates multiple pairs of charge carriers. We observed highly efficient generation of electron-hole pairs due to impact excitation in single-walled carbon nanotube p-n junction photodiodes. Optical excitation into the second electronic subband E22 leads to striking photocurrent steps in the device I-VSD characteristics that occur at voltage intervals of the band-gap energy EGAP/e. Spatially and spectrally resolved photocurrent combined with temperature-dependent studies suggest that these steps result from efficient generation of multiple electron-hole pairs from a single hot E22 carrier. This process is both of fundamental interest and relevant for applications in future ultra-efficient photovoltaic devices.

https://www.lassp.cornell.edu/lassp_data/mceuen/homepage/Publications/Gabor_Science_2009_supmat.pdf

Supporting Online Material for Extremely Efficient Multiple Electron-Hole Pair Generation in Carbon Nanotube Photodiodes

Freestanding synaptic transistors are fabricated on solution-processed chitosan membranes. A short-term memory to long-term memory transition is observed due to proton-related electrochemical doping under repeated pulse stimulus. Moreover, freestanding artificial synaptic devices with multiple presynaptic inputs are investigated, and spiking logic operation and logic modulation are realized.

Freestanding Artificial Synapses Based on Laterally Proton‐Coupled Transistors on Chitosan Membranes

Proton-conducting graphene oxide electrolyte films with very high electric-double-layer capacitance are used as the gate dielectrics for oxide-based neuron transistor fabrication. Paired-pulse facilitation, dendritic integration, and orientation tuning are successfully emulated. Additionally, neuronal gain controls (arithmetic) are also experimentally demonstrated. The results provide a new-concept approach for building brain-inspired cognitive systems.

Proton-Conducting Graphene Oxide-Coupled Neuron Transistors for Brain-Inspired Cognitive Systems.

Hardware implementation of artificial synapse/neuron by electronic/ionic hybrid devices is of great interest for brain-inspired neuromorphic systems. At the same time, printed electronics have received considerable interest in recent years. Here, printed dual-gate carbon-nanotube thin-film transistors with very high saturation field-effect mobility (≈269 cm2 V−1 s–1) are proposed for artificial synapse application. Some important synaptic behaviors including paired-pulse facilitation (PPF), and signal filtering characteristics are successfully emulated in such printed artificial synapses. The PPF index can be modulated by spike width and spike interval of presynaptic impulse voltages. The results present a printable approach to fabricate artificial synaptic devices for neuromorphic systems.

Printed Neuromorphic Devices Based on Printed Carbon Nanotube Thin-Film Transistors

Flexible metal oxide/graphene oxide hybrid multi-gate neuromorphic transistors are fabricated on flexible conducting graphene substrates. Dendritic integrations in both spatial and temporal modes are emulated, and spatiotemporal correlated logics are obtained. A proof-of-principle visual system model for emulating Lobula Giant Motion Detector neuron is also investigated. The results are of great significance for flexible sensors and neuromorphic cognitive systems.

Flexible Metal Oxide/Graphene Oxide Hybrid Neuromorphic Transistors on Flexible Conducting Graphene Substrates.

Recent progress in using biomaterials to fabricate functional electronics has got growing attention for the new generation of environmentally friendly and biocompatible electronic devices. As a kind of biological material with rich source, proteins are essential natural component of all organisms. At the same time, artificial synaptic devices are of great significance for neuromorphic systems because they can emulate the signal process and memory behaviors of biological synapses. In this report, natural chicken albumen with high proton conductivity was used as the coupling electrolyte film for organic/inorganic hybrid synaptic devices fabrication. Some important synaptic functions including paired-pulse facilitation, dynamic filtering, short-term to long-term memory transition and spatial summation and shunting inhibition were successfully mimicked. Our results are very interesting for biological friendly artificial neuron networks and neuromorphic systems.

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Ping Feng

Papers

Freestanding Artificial Synapses Based on Laterally Proton‐Coupled Transistors on Chitosan Membranes

Proton-Conducting Graphene Oxide-Coupled Neuron Transistors for Brain-Inspired Cognitive Systems.

Printed Neuromorphic Devices Based on Printed Carbon Nanotube Thin-Film Transistors

Flexible Metal Oxide/Graphene Oxide Hybrid Neuromorphic Transistors on Flexible Conducting Graphene Substrates.

Artificial Synaptic Devices Based on Natural Chicken Albumen Coupled Electric-Double-Layer Transistors