記述言語：英語   掲載種別：研究論文（学術雑誌）

This paper proposes a nanoparticle-based atomic switch network memristive device, capable of both volatile and nonvolatile switching operations, which have not been previously reported for this material. The operational modes can be determined by altering the compliance current, demonstrating high stability over 100 cycles. Analysis of the conduction mechanism using I–V curves reveals switching characteristics consistent with space-charge-limited current conduction during the set process and ohmic behavior in the reset state. Furthermore, this study analyzes these dual-operational modes in devices with varying electrode spacings. The results indicate that a wider spacing necessitated a higher compliance current for the volatile-to-nonvolatile transition, underscoring the significance of interconnection. These findings facilitate the integration of neuron and synapse functions within a single atomic switch network device, thereby advancing neuromorphic systems.

DOI： 10.1002/aelm.202300709

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The synaptic plasticity of the Ag-Ag2S nanoparticle-based volatile memristor system is demonstrated. The nanoparticles self-assemble into a network with over 103 interconnected atomic switch interfaces. Short-term plasticity is identified by spontaneous conductance relaxation, attributed to the memristor's volatility. The conductance of the network is enhanced when a subsequent stimulus pulse arrives shortly after the previous one, analogous to the paired-pulse facilitation in biological synapses. Furthermore, repeated pulse stimulation is used to achieve the transition from short-term plasticity to long-term potentiation, a process related to learning and memory formation. Remarkably, the result reveals that the lifetime of long-term potentiation for 100-pulse stimulation is 40 min, indicating that the device can forget newly acquired information after prolonged storage, akin to human memories. The findings provide insight into the the learning and memory abilities of atomic switch network memristors, facilitating the development of hardware-implemented artificial neural networks.

DOI： 10.1002/aelm.202400360

Scopus

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Computation performance of in-materio reservoir device was evaluated by varying intensity of noise injection. Materials for the reservoir device was synthesized using a α-Fe2O3/titanium bismuth oxide composite by using the sol-gel method. The prepared samples were characterized by conducting X-ray diffractmetry, transmission electron microscopy, and energy dispersive X-ray spectroscopy to confirm presence of α-Fe2O3, TiO2, and Bi4Ti3O12 nanoparticles. The I-V and V-t curves show nonlinearity, and phase differences between input and output signals, and the fast Fourier transform of the V-t curve showed high harmonics at the input sine wave with 11 Hz of frequency. In the waveform prediction task, the prediction accuracy was improved only when a small intensity of white noise voltage was superimposed to the input information signal.

DOI： 10.35848/1347-4065/acbd5b

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Integrating sensory devices with wireless power transfer technology for remote sensing (RS) requires the implementation of complex electronic circuitry and communication protocols. To overcome this challenge and remotely monitor mechanical force, we directly integrated piezo-responsive porous multiwalled carbon nanotubes (MWCNTs)/polydimethylsiloxane (PDMS) nanocomposites with a near-field wireless power transfer system. The wireless system transfers power bidirectionally between the transmitter and the sensing receiver at the resonant frequency of 13.56 MHz. The detection principle is based on the mechanical force-induced impedance changes in the receiver circuit. The modulated impedance signal is detected wirelessly at the transmitter circuit via a full-bridge rectifier and a smoothing capacitor. Furthermore, we demonstrate the wireless monitoring of finger bending and applied force using our flexible and disposable sensor without using any energy storage devices. The results suggest a response and recovery time of 400 ± 50 ms, strain sensitivity of 24.73, and pressure sensitivity of 0.98. Our approach adds a new path for disposable haptic-based sensory applications that do not require complex communication protocols in medical, robotics, and other fields.

DOI： 10.1109/JSEN.2023.3248021

Scopus

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：記事・総説・解説・論説等（商業誌、新聞、ウェブメディア）

記述言語：英語   掲載種別：研究論文（学術雑誌）

For scientists in numerous fields, creating a physical device that can function like the human brain is an aspiration. It is believed that we may achieve brain-like spatiotemporal information processing by fabricating an in materio reservoir computing (RC) device because of a complex random network topology with nonlinear dynamics. One of the significant drawbacks of a two-dimensional physical reservoir system is the difficulty in controlling the network density. This work reports the use of a 3D porous template as a scaffold to fabricate a three-dimensional network of a single-walled carbon nanotube polyoxometalate nanocomposite. Although the three-dimensional system exhibits better nonlinear dynamics and spatiotemporal dynamics, and higher harmonics generation than a two-dimensional system, the results suggest a correlation between a higher number of resistive junctions and reservoir performance. We show that by increasing the spatial dimension of the device, the memory capacity improves, while the scale-free network exponent (γ) remains nearly unchanged. The three-dimensional device also displays improved performance in the well-known RC benchmark task of waveform generation. This study demonstrates the impact of an additional spatial dimension, network distribution and network density on in materio RC device performance and tries to shed some light on the reason behind such behavior.

DOI： 10.1039/d2nr04619a

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

An Ag2Se nanowire random network was fabricated for application as a data augmentation device and combined with a binary convolutional neural network (BCNN) to achieve high accuracy in voice classification tasks. Due to the nonlinear high-dimensional characteristics resulting from the formation of the conductive filament at the cross junction, the Ag2Se device could transform input data into higher-order multiple signals, thereby enhancing the accuracy of the classification task by augmenting input signals. The results indicate that materials can realize data augmentation with the same performance as software, suggesting that material-based hardware can be used as an elemental technology for information processing.

DOI： 10.35848/1882-0786/acae6a

Scopus

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

This study aims to implement a reservoir-based convolutional neural network (CNN) on physical reservoir computing (RC) to develop an efficient image recognition system for edge AI. Therefore, we propose a novel reservoir-based convolution circuit system that uses in-material reservoir computing, a type of physical RC made from a sulfonated polyaniline network. The experimental results demonstrate that the proposed circuit system extracts image features in the same way as the original CNN and that a reservoir-based CNN on the in-material RC achieves an accuracy rate of 81.7% in an image classification task while an echo state network-based CNN achieves 87.7%.

DOI： 10.1109/ISCAS46773.2023.10181436

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The need for highly energy-efficient information processing has sparked a new age of material-based computational devices. Among these, random networks (RNWs) of carbon nanotubes (CNTs) complexed with other materials have been extensively investigated owing to their extraordinary characteristics. However, the heterogeneity of CNT research has made it quite challenging to comprehend the necessary features of in-materio computing in a RNW of CNTs. Herein, we systematically tackle the topic by reviewing the progress of CNT applications, from the discovery of individual CNT conduction to their recent uses in neuromorphic and unconventional (reservoir) computing. This review catalogues the extraordinary abilities of random CNT networks and their complexes used to conduct nonlinear in-materio computing tasks as well as classification tasks that may replace current energy-inefficient systems.

DOI： 10.1088/2634-4386/ac676a

DOI： 10.1088/2634-4386/ac676a

Scopus

その他リンク： https://iopscience.iop.org/article/10.1088/2634-4386/ac676a

記述言語：英語   掲載種別：研究論文（学術雑誌）

A Ag2S-island network is fabricated with surrounding electrodes to enable it to be used as a reservoir for unconventional computing. Local conductance change occurs due to the growth/shrinkage of Ag filaments from/into each Ag2S island in the reservoir. The growth/shrinkage of Ag filaments is caused by the drift of Ag+ cations in each Ag2S island, which results in a unique non-linear response as a reservoir, especially at lower frequencies. The response of the reservoir is shown to depend on the frequency and amplitude of the input signals. So as to evaluate its capability as a reservoir, logical operations were performed using the subject Ag2S-island network, with the results showing an accuracy of greater than 99%.

DOI： 10.1039/D2NR01439D

DOI： 10.1039/D2NR01439D

Scopus

その他リンク： https://pubs.rsc.org/en/content/articlelanding/2022/NR/D2NR01439D

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1002/aisy.202100145

記述言語：英語   掲載種別：研究論文（学術雑誌）

A method for room temperature demonstration of in-materio reservoir computing (RC) with a single-walled carbon nanotube/porphyrin-polyoxometalate network (SWNT/Por-POM) is proposed. Boolean functions of OR, AND, NOR, NAND, XOR, and XNOR, all were reconstructed with an accuracy >90% via supervised training of linear voltage readouts. The RC pre-requisite of echo-state property and recurrent connection allowed for consistent performances over multiple test datasets and time-shifted target sequences. Moreover, a non-zero machine intelligence index confirmed the presence of negative differential resistance dynamics, incorporating in SWNT/Por-POM the mathematical equivalence of additive and subtractive functions, thereby aiding the construction of such complex Boolean functions.

DOI： 10.35848/1882-0786/ac24db

Scopus

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

A sulfonated polyaniline (SPAN) organic electrochemical network device (OEND) is fabricated using a simple drop-casting method on multiple Au electrodes for use in reservoir computing (RC). The SPAN network has humidity-dependent electrical properties. Under high humidity, the SPAN OEND exhibits mainly ionic conduction, including charging of an electric double layer and ionic diffusion. The nonlinearity and hysteresis of the current–voltage characteristics progressively increase with increasing humidity. The rich dynamic output behavior indicates wide variations for each electrode, which improves the RC performance because of the disordered network. For RC, waveform generation and short-term memory tasks are realized by a linear combination of outputs. The waveform task accuracy and memory capacity calculated from a short-term memory task reach 90% and 33.9, respectively. Improved spoken-digit classification is realized with 60% accuracy by only 12 outputs, demonstrating that the SPAN OEND can manage time series dynamic data operation in RC owing to a combination of rich dynamic and nonlinear electronic properties. The results suggest that SPAN-based electrochemical systems can be applied for material-based computing, by exploiting their intrinsic physicochemical behavior.

DOI： 10.1002/adma.202102688

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Reservoir computing (RC), a low-power computational framework derived from recurrent neural networks, is suitable for temporal/sequential data processing. Here, we report the development of RC devices utilizing Ag-Ag2S core-shell nanoparticles (NPs), synthesized by a simple wet chemical protocol, as the reservoir layer. We examined the NP-based reservoir layer for the required properties of RC hardware, such as echo state property, and then performed the benchmark tasks. Our study on NP-based reservoirs highlighted the importance of the dynamics between the NPs as indicated by the rich high dimensionality due to the echo state property. These dynamics affected the accuracy (up to 99%) of the target waveforms that were generated with a low number of readout channels. Our study demonstrates the great potential of Ag-Ag2S NPs for the development of next-generation RC hardware.

DOI： 10.35848/1347-4065/abe206

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Liquid metals have attracted attention as functional components for moldable electronics, such as soft flexible connectors, wires or conductive ink. The relatively high surface tension (> 400 mN m−1) and the fact that liquid metals do not readily wet ceramic or oxide surfaces have led to devising unique techniques to spread the liquid and mold its shape. These techniques include surface modification, electrowetting and vacuum filling of channels. This work presents an injection technique based on pressurized fountain pen lithography with glass nanopipettes developed to directly pattern liquid metal on flat hard substrates. The liquid metals were eutectic alloys of Gallium, including Gallium-Indium (EGaIn), Gallium-Indium-Zinc and Gallium-Indium-Tin. The nanopipettes were coated internally with gold, acting as a sacrificial layer and facilitating the wetting of the pipette down to its pore, with an inner diameter of ~ 100–300 nm. By applying hydrodynamic pressure to the connected end of the pipette, the metal was extruded through the pore, forming long continuous (> 3 mm) and narrow (~ 1–15 µm) metal lines on silicon oxide and gold surfaces at room temperature and ambient conditions. With this robust platform, it is possible to pattern liquid metals on a variety of substrates and geometries down to the micron range.

DOI： 10.1038/s41598-021-84065-4

Scopus

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記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）

<p>PCBM薄膜上に少量の金を蒸着するとコンダクタンスが顕著に増加する現象を見出した。この金蒸着量では金自体のアイランド成長に伴う多重トンネル伝導は起こりえないので、金蒸着したPCBM薄膜では異なるメカニズムによる電気伝導が起きていると考えられる。このような顕著なコンダクタンス増加の起源は明らかではないが、金がPCBM薄膜のドーパントとして働く可能性がある。講演では分光学的なデータも示し議論を行う。</p>

DOI： 10.14886/jvss.2020.0_267

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/130007959460

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2020 The Japan Society of Applied Physics We succeeded in bridging unzipped graphene nanoribbons (GNRs) and separating them from unwanted single-walled carbon nanotubes (SWNTs) using a frequency-dependent dielectrophoresis (DEP) method by varying the frequency and applied voltage used for future assembly. Atomic force micrographs and Raman spectra proved that unzipped GNRs were successfully bridged by the DEP method at frequencies higher than 13 MHz. The theoretical calculation also supported the finding that only GNRs were collected from a mixture of SWNTs/GNRs suspensions.

DOI： 10.35848/1882-0786/abb68d

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2020 IOP Publishing Ltd. Electronic noise generators are an essential component of molecular neuromorphic devices. To realize molecular noise generators with a high degree of freedom for design and integration into molecular devices, the utilization of the local electric field for the modulation of electrical conduction via a shape-limited conductive polymer is one promising strategy. Herein, a molecular noise generator composed of thin self-doped polyaniline (SPAN) lines is reported. SPAN lines fabricated via fountain pen lithography on SiO2/Si substrates were found to generate current noise upon laser irradiation. This current noise exhibited white-noise-like power spectral density in the frequency range of 1-25 Hz and was independent of temperature. Multiple independent noise generation on the same substrate was also successfully demonstrated. The present results indicate that the noise generation mechanism involves the local modulation of hopping conduction via SPAN lines owing to the spatial proximity of the conduction path in the SPAN line to the surface photovoltage region of the SiO2/Si interface. This on-site random noise generation in shape-limited conductive polymers is expected to be beneficial for the realization of molecular neuromorphic devices.

DOI： 10.1088/1361-6528/ab96e4

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2020 American Chemical Society. Charge dynamics play an important role in numerous natural phenomena and artificial devices, and tracking charge migration and recombination is crucial for understanding the mechanism and function of systems involving charge transfer. Tip-synchronized pump-probe electrostatic force microscopy simultaneously permits highly sensitive detection, microsecond time resolution, and nanoscale spatial resolution, where the spatial distribution in static measurement (usual EFM) reflects differences in the carrier density and the time evolution reveals the surface carrier mobility. By using this method, carrier injection and ejection in sulfonated polyaniline (SPAN) thin films were visualized. Comparison of tr-EFM results of SPAN thin films with different doping levels revealed the individual differences in carrier density and mobility.

DOI： 10.1021/acs.jpca.9b12017

Scopus

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記述言語：日本語   掲載種別：研究論文（学術雑誌）

<p>リザバーコンピューティング(RC)は、リザバー層で行われる演算を物理現象に置換することができる情報処理システムである。我々は、自己ドープ型ポリアニリン分子(SPAN)と Au ナノ粒子(AuNP)からなるネットワーク内に非線形 <i>I-V </i>特性が発生することを明らかにしている。本研究では、RCへの適用可能性を探るため、ナノギャップ電極によって多入力多出力電極間での非線形電気特性および記憶特性を検討した。</p>

DOI： 10.14886/jvss.2020.0_268

CiNii Article

CiNii Research

その他リンク： https://ci.nii.ac.jp/naid/130007959456

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2017 The Japan Society of Applied Physics. We investigated the electrical properties of a two-dimensional (2D) network consisting of multiple Au nanoparticles (AuNPs) and self-doped polyaniline sulfonate (SPAN). Nonlinear current-voltage (I-V) characteristics with wide variations were observed in the networks. The temperature dependence of the I-V characteristics exhibited a short localization length, suggesting conjugated electronic properties of the AuNP-SPAN network. This result provides a new direction for network-based molecular electronic devices.

DOI： 10.7567/JJAP.56.128001

Scopus

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2016 Author(s). The conduction behavior of ultrathin films (about 10 nm thick) composed of self-doped water-soluble polyaniline sulfonate (SPAN) was investigated using nano-gap electrodes under vacuum conditions. The conductance was found to be ohmic even in the high field regime up to 105V cm-1 over a temperature range of 10-300 K. The temperature dependence of the conductance indicated that SPAN gave the extremely high value of localization length (L) = 300 nm without secondary doping, in comparison with conventional polyaniline. We propose that SPAN forms long-range highly crystalline metallic grains, and we observed intra-grain conduction due to some grains directly bridging the two nano-gap electrodes at low temperature. We conclude that inter-grain conduction becomes dominant as the temperature increases.

DOI： 10.1063/1.4961610

Scopus

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開催期間： 2022年03月22日 - 2022年03月26日   記述言語：日本語  

開催期間： 2021年12月16日 - 2021年12月20日   記述言語：英語  

開催期間： 2021年10月26日 - 2021年10月29日   記述言語：英語  

開催期間： 2021年05月20日 - 2021年05月22日   記述言語：日本語  

開催期間： 2021年03月16日 - 2021年03月19日   記述言語：日本語  

開催期間： 2020年12月09日 - 2020年12月11日   記述言語：日本語  

開催期間： 2020年11月09日 - 2020年11月12日   記述言語：英語  

開催期間： 2020年09月08日 - 2020年09月11日   記述言語：英語  

開催期間： 2020年07月23日 - 2020年07月24日   記述言語：日本語  

出願番号：2020-174660  出願日：2020年10月16日