Advances in memristor based artificial neuron fabrication-materials,models,and applications

Spiking neural network(SNN),widely known as the third-generation neural network,has been frequently investigated due to its excellent spatiotemporal information processing capability,high biological plausibility,and low energy consumption characteristics.Analogous to the working mechanism of human brain,the SNN system transmits information through the spiking action of neurons.Therefore,artificial neurons are critical building blocks for constructing SNN in hardware.Memristors are drawing growing attention due to low consumption,high speed,and nonlinearity characteristics,which are recently introduced to mimic the functions of biological neurons.Researchers have proposed multifarious memristive materials including organic materials,inorganic materials,or even two-dimensional materials.Taking advantage of the unique electrical behavior of these materials,several neuron models are successfully implemented,such as Hodgkin–Huxley model,leaky integrate-and-fire model and integrate-and-fire model.In this review,the recent reports of artificial neurons based on memristive devices are discussed.In addition,we highlight the models and applications through combining artificial neuronal devices with sensors or other electronic devices.Finally,the future challenges and outlooks of memristor-based artificial neurons are discussed,and the development of hardware implementation of brain-like intelligence system based on SNN is also prospected.

Non-isothermal crystallization kinetics of Nylon 10T and Nylon 10T/1010 copolymers:Effect of sebacic acid as a third comonomer

Nylon 10 T and Nylon 10T/1010 samples were synthesized by direct melt polymerization. The non-isothermal crystallization kinetics of Nylon 10 T and Nylon 10T/1010 was investigated by means of differential scanning calorimetry(DSC). Jeziorny equation and Mo equation were applied to describe the non-isothermal crystallization kinetics of the Nylon 10 T and the Nylon 10T/1010. The activation energies for non-isothermal crystallization were obtained by Vyazovkin's method and Friedman's method, respectively. These results showed that Jeziorny equation and Mo equation well described the non-isothermal crystallization kinetics of the Nylon 10 T and the Nylon 10T/1010. It was found that the values of the activation energy for non-isothermal crystallization of the Nylon 10T/1010 were lower than those of the Nylon 10 T at a given temperature or relative crystallinity degree,which revealed that crystallization ability of the Nylon 10T/1010 was higher. The crystal morphology was observed by means of a polarized optical microscope(POM) and X-ray diffraction(XRD). It was found that the addition of sebacic acid comonomer not only did not change the crystal form of the Nylon 10 T, but also significantly increased the number and decreased the size of spherulites. Comparing with the Nylon 10 T, the crystallization rate was increased with the addition of the sebacic acid comonomer.

Neuroprotection of phenolic alkaloids from Menispermum dauricum versus melatonin against oxygen-glucose-serum-deprivation-mediated injury

BACKGROUND： Recent studies have demonstrated that phenolic alkaloids from Menispermum dauricum （PAMD） can protect the heart and brain from ischemia/reperfusion injury, and promote neuron survival by inhibiting neuronal Bax and upregulating Bcl-2 expression following ischemia/reperfusion. OBJECTIVE： To investigate the neuroprotective effects of PAMD versus exogenous melatonin against ischemia/reperfusion injury. DESIGN, TIME AND SETTING： Observation and comparison experiments at a cellular level were performed at the Department of Biochemistry and Molecular Biology, Tongji Medical College of Huazhong University of Science and Technology between February 2007 and February 2008. MATERIALS： PAMD （95% purity） was provided by Kunming Institute of Botany, Chinese Academy of Sciences; melatonin was provided by Sigma, USA. METHODS： N2a mouse neuroblastoma cells were cultured in vitro deprived of glucose, serum and oxygen for 90 minutes, then cultured in normal medium containing different concentrations of PAMD （0.1, 1.0, 10 mg/L） or melatonin （1, 10, and 100 μmol/L）. Cells cultured in normal conditions served as a control. MAIN OUTCOME MEASURES： The culture solution was collected to determine the content of ex- citatory neurotransmitters such as glutamic acid and aspartic acid; cell viability was detected by MTT methods; reactive oxygen species production was determined by fluorescence spectroscopy; mito- chondrial transmembrane potential （？Ψm） was detected by laser confocal scanning; cytochrome C was measured by western blotting; and caspase-3 activity was determined by visible spectropho- tometry. RESULTS： Melatonin and PAMD both promoted oxygen-glucose-serum deprivation-mediated N2a cell survival （P 〈 0.01） and inhibited glutamic acid release （P 〈 0.01）, but melatonin did not inhibit aspartic acid production. The protective effects were the strongest using melatonin 100 μmol/L and PAMD 10 mg/L, so subsequent experiments were the performed at those doses. Although PAMD could no longer maintain mitochondrial transmembrane potential 6 hours after reperfusion, its in- hibitory effects on cytochrome C release from mitochondria and scavengers of reactive oxygen species were stronger than those of melatonin （P 〈 0.01）. However, its inhibitory effect on caspase-3 activity was weaker than that of melatonin： PAMD could inhibit caspase-3 activity 12 hours after reperfusion （P 〈 0.01）, but melatonin inhibited caspase-3 activity 28 hours after reperfusion （P 〈 0.01）. CONCLUSION： The results show that melatonin and PAMD have neuroprotective effects, but that the mechanisms are varied. Melatonin can maintain mitochondrial transmembrane potential, but its inhibitory effects on cytochrome C release, caspase-3 activity, and reactive oxygen species scav-enging are different from those of PAMD.

Neutron irradiation-induced effects on the reliability performance of electrochemical metallization memory devices

In this work,electrochemical metallization memory(ECM)devices with an Ag/AgInSbTe(AIST)/amorphous carbon(a-C)/Pt structure were irradiated with 14 MeV neutrons.The switching reliability performance before and after neutron irradiation was compared and analyzed in detail.The results show that the irradiated memory cells functioned properly,and the initial resistance,the resistance at the low-resistance state(LRS),the RESET voltage and the data retention performance showed little degradation even when the total neutron fluence was as high as 2.5×1011 n/cm2.Other switching characteristics such as the forming voltage,the resistance at the high-resistance state(HRS),and the SET voltage were also studied,all of which merely showed a slight parameter drift.Irradiation-induced Ag ions doping of the a-C layer is proposed to explain the damaging effects of neutron irradiation.The excellent hard characteristics of these Ag/AIST/a-C/Pt-based ECM devices suggest potential beneficial applications in the aerospace and nuclear industries.

Voltage-dependent plasticity and image Boolean operations realized in a WOx-based memristive synapse

The development of electronic devices that possess the functionality of biological synapses is a crucial step towards neuromorphic computing.In this work,we present a WOx-based memristive device that can emulate voltage-dependent synaptic plasticity.By adjusting the amplitude of the applied voltage,we were able to reproduce short-term plasticity(STP)and the transition from STP to long-term potentiation.The stimulation with high intensity induced long-term enhancement of conductance without any decay process,thus representing a permanent memory behavior.Moreover,the image Boolean operations(including intersection,subtraction,and union)were also demonstrated in the memristive synapse array based on the above voltage-dependent plasticity.The experimental achievements of this study provide a new insight into the successful mimicry of essential characteristics of synaptic behaviors.

Emerging multimodal memristors for biorealistic neuromorphic applications

The integration of sensory information from different modalities,such as touch and vision,is essential for organisms to perform behavioral functions such as decision-making,learning,and memory.Artificial implementation of human multi-sensory perception using electronic supports is of great significance for achieving efficient human–machine interaction.Thanks to their structural and functional similarity with biological synapses,memristors are emerging as promising nanodevices for developing artificial neuromorphic perception.Memristive devices can sense multidimensional signals including light,pressure,and sound.Their in-sensor computing architecture represents an ideal platform for efficient multimodal perception.We review recent progress in multimodal memristive technology and its application to neuromorphic perception of complex stimuli carrying visual,olfactory,auditory,and tactile information.At the device level,the operation model and undergoing mechanism have also been introduced.Finally,we discuss the challenges and prospects associated with this rapidly progressing field of research.

Self-powered and broadband opto-sensor with bionic visual adaptation function based on multilayer γ-InSe flakes

Visual adaptation that can autonomously adjust the response to light stimuli is a basic function of artificial visual systems for intelligent bionic robots.To improve efficiency and reduce complexity,artificial visual systems with integrated visual adaptation functions based on a single device should be developed to replace traditional approaches that require complex circuitry and algorithms.Here,we have developed a single two-terminal opto-sensor based on multilayer γ-InSe flakes,which successfully emulated the visual adaptation behaviors with a new working mechanism combining the photo-pyroelectric and photo-thermoelectric effect.The device can operate in self-powered mode and exhibit good human-eye-like adaptation behaviors,which include broadband light-sensing image adaptation(from ultraviolet to near-infrared),near-complete photosensitivity recovery(99.6%),and synergetic visual adaptation,encouraging the advancement of intelligent opto-sensors and machine vision systems.

Memristors with organic-inorganic halide perovskites

Organic-inorganic halide perovskites(OHPs)have been intensively studied for application in solar cells with high conversion efficiency exceeding 22%.The unique electrical and optical properties of OHPs have led to their use in optoelectronic device applications beyond photovoltaics,such as light-emitting diodes,photodetectors,transistors.New information storage technologies and computing architectures are being researched extensively with the aim of addressing the growing challenge of approaching end of Moore's law and von Neumann bottleneck.As the fourth basic circuit element,memristor is a leading candidate with powerful capabilities in information storage and neuromorphic computing applications.Recently,OHPs have received growing attention as promising materials for memristors.In particular,their mixed ionic-electronic conduction ability paired with light sensitivity provide OHPs with the opportunity to display novel functions such as optical-erase memory,optogenetics-inspired synaptic functions,and lightaccelerated learning capability.This review covers recent advances in OHP-based memristors development including memristive mechanism and analytical models,universal memristive characteristics for memory and neuromorphic computing applications,and novel multi-functionalization.Challenges and future prospects of OHP-based memristors are also discussed.