<jats:p>A random network of Ag/Ag2S nanoparticles (NPs) was used as a physical system in reservoir computing (RC) because the network has nonlinear and dynamical characteristics. Ag/Ag2S NPs were synthesized by the modified Brust–Schiffrin method. Atomic switching among the NPs caused nonlinear dynamical behavior of the random network. The Fourier transform of output signals indicated that the generated harmonics were far higher with a larger amplitude of the input sine wave because the atomic switching occurred only at high bias voltages. Higher accuracy was achieved in the Boolean logic RC task because of the nonlinearity originating from switching. These findings suggest that nonlinearity plays a fundamental role in the design and implementation of RC devices.</jats:p>

The importance of haptic in-sensor computing devices has been increasing. Herein, a haptic sensor with a hierarchical structure is successfully fabricated via the sacrificial template method, using carbon nanotube-polydimethylsiloxane (CNT-PDMS) nanocomposites for in-sensor computing applications. The CNT-PDMS nanocomposite sensors, with different sensitivities, are obtained by varying the amount of CNTs. The input stimuli are transformed into higher-dimensional information, enabling a new path for the CNT-PDMS nanocomposite application, which is implemented on a robotic hand as an in-sensor computing device by applying a reservoir computing paradigm. The nonlinear output data obtained from the sensors are trained using linear regression and used to classify nine different objects used in everyday life with an object recognition accuracy of >80% for each object. This approach can enable tactile sensation in robots while reducing the computational cost.

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.

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.

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.

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.

A method for room temperature demonstration of in-materio reservoir computing (RC) with 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.

This paper presents the results of morphological study on nanosized nickel zinc ferrite (NZF) thick film using linseed oil as organic vehicle and nanosized NZF powder. First, NZF nanopowder is mixed with organic vehicle which consists of linseed oil, m-xylene and α-terpineol. Paste samples were screen printed onto alumina as substrate, dried and fired at different temperatures of 100°C, 200°C, and 300°C, respectively. Microscopic images of the samples and elemental analysis were observed to determine good dispersion of the active powder with the organic vehicle. Based on the results, the nanoparticles were uniformly dispersed, and images of thick films fired at 200°C and 300°C have shown clearly visible particles, indicating that at these temperatures, the organic vehicle has started to evaporate on the surface, revealing nanoparticles of the active powders. The elemental analysis confirmed this idea, of which carbon element of the organic vehicle gradually decreased with increasing temperature.

In this paper, nickel zinc ferrite (NZF) nanopowder was mixed with organic vehicle which consists of linseed oil, m-xylene and α-terpineol. Then the mixture was sonicated for 1 hour at 40°C in order to obtain homogenous paste, followed by printing it onto FR4 substrate using the screen printing technique to form the NZF thick film layer before dried at 100°C and later fired at 200°C. A basic square shape patch antenna by using silver paste was printed onto the NZF thick film layer and was compared with another patch antenna which was been printed without the NZF layer. The results showed that the antenna with NZF thick film layer has return loss of -10.97dB, resonant frequency 6.42GHz, bandwidth 3.9 and Q factor of 1.646, which is better compared to the antenna without the layer by 32.81%, 3.22%, 86.60% and 44.69% respectively.

Research on microstrip patch antenna (MPA) has been growing in the past few decades due to its planar profile and easy fabrication. Its simplicity of structure, which includes a conductive patch, a dielectric substrate, a ground plane, and a microstrip feeder, is making it more popular for integration in devices which are more focused on miniaturization and flexibility. There are, however, a few disadvantages of MPA, such as narrow bandwidth, low power, and limited inexpensive material selection if a current printed circuit board etching fabrication technique is used. Ferrite substrates are known to be able to help overcome this issue, but the properties of bulk ferrites are difficult to control. This paper aims to solve this problem by using thick-film technology, which utilizes a screen printing method to include ferrite thick film in the MPA structure as substrate overlay to help enhance the performance of MPA. Yttrium iron garnet was chosen as the starting ferrite nanopowders, and the preparation and characterization of the ferrite thick-film paste were carried out to investigate properties of the thick film. Results showed that the thick film showed moderate permittivity and permeability, which is suitable for MPA fabrication. The actual fabricated MPA with ferrite thick-film inclusion on FR4 substrate showed that the thick film improved the performance of MPA with low firing temperature of 200 °C. For MPA which is designed to work at 5.8 GHz, the return loss and -3-dB bandwidth improved 100% and 73%, respectively. In conclusion, ferrite thick-film inclusion in MPA fabrication has proven to improve the performance of the antenna in terms of return loss and bandwidth enhancement.

Discovery of carbon nanotubes (CNTs) was beginning of a revolutionary path for material scientists. CNTs extraordinary properties made this wonder material an important alternative for scientists in all fields; although utilizing CNTs were not as simple as synthesizing them. Ever since the discovery, numerous platforms for synthesis of CNTs have been investigated. Depending on the necessity of the application in which CNTs are exploited different quality, yield, chirality, size, and properties are required. Nowadays the fabrication process mostly relies on arc discharge, laser ablation and chemical vapor deposition (CVD). One of the major drawbacks in exploitation of CNTs is their tenancy to aggregate due to the weak van der Waals forces present as a result of sp2 hybridization of carbon atoms. Due to the extraordinary mechanical, electrical, optical, chemical, physical, biological, and other features of CNTs, scientists began to work on different methods to overcome aggregation during utilization of CNTs. Dispersion of CNTs has been done via several functionalization processes. Each of these techniques has their own functionality. Functionalization of CNTs depends on two central techniques, covalent and noncovalent modifications, which are essential, to achieve desired characteristics that can be applied in wide range of applications. Therefore, in this chapter we will try to explain the CNTs fabrication techniques as well as the methods that have been utilized to increase the purity and dispersion of CNTs.

Abstract In this work, we reported a chemically modified technique via screen printing method to fabricate carbon nanotubes (CNTs)/Polydimethylsiloxane (PDMS) nanocomposite to monitor the piezoresistive behavior of nanocomposite while applying pressure. Raman, UV/vis and HRTEM results were utilized to verify the quality of CNTs, purified through chemical and physical treatments; carboxylic and hydroxylic functional groups were determined via FTIR. The optimum dispersion ratio of the nanocomposite was observed by FESEM images which clearly show the consistent dispersion of CNTs coated by PDMS. Furthermore, I–V characterization of the developed nanocomposite indicates change in resistivity for a few orders of magnitude before and after treatment in addition to resistance variation as a result of different applied pressures. These results indicate the importance of CNTs treatment prior to nanocomposite fabrication in order to obtain lower percolation threshold. Obtained results are useful in development of haptic sensor, artificial finger, and brain like devices for robotics applications.

Haptic sensors are essential devices that facilitate human-like sensing systems such as implantable medical devices and humanoid robots. The availability of conducting thin films with haptic properties could lead to the development of tactile sensing systems that stretch reversibly, sense pressure (not just touch), and integrate with collapsible. In this study, a nanocomposite based hemispherical artificial fingertip fabricated to enhance the tactile sensing systems of humanoid robots. To validate the hypothesis, proposed method was used in the robot-like finger system to classify the ripe and unripe tomato by recording the metabolic growth of the tomato as a function of resistivity change during a controlled indention force. Prior to fabrication, a finite element modeling (FEM) was investigated for tomato to obtain the stress distribution and failure point of tomato by applying different external loads. Then, the extracted computational analysis information was utilized to design and fabricate nanocomposite based artificial fingertip to examine the maturity analysis of tomato. The obtained results demonstrate that the fabricated conformable and scalable artificial fingertip shows different electrical property for ripe and unripe tomato. The artificial fingertip is compatible with the development of brain-like systems for artificial skin by obtaining periodic response during an applied load.

In this work, a quick and effective method to synthesize carbon nanotubes (CNTs) is reported; a commercial microwave oven of 600 W at 2.45 GHz was utilized to synthesize CNTs from plasma catalytic decomposition of polyethylene. Polyethylene and silicon substrate coated with iron (III) nitrate were placed in the reaction chamber to form the synthesis stock. The CNTs were synthesized at 750°C under atmospheric pressure of 0.81 mbar. Raman spectroscopy and field emission scanning electron microscope revealed the quality and entangled bundles of mixed CNTs from which the diameters of the CNTs were calculated to be between 1.03 and 25.00 nm. High resolution transmission electron microscope further showed that the CNTs obtained by this method are graphitized. Energy dispersive X-ray analysis and thermogravimetric analysis revealed above 98% carbon purity.

Advances in the synthesis of carbon nanotubes (CNTs) have emerged as a result of the properties and potential application of carbon nanotubes. We demonstrated a simple approach of using domestic microwave oven with 600W at 2.45 GHz which was modified to produce CNTs from a carbon source on coated silicon oxide substrate. The Raman spectroscopy showed the graphitic nature of the obtained CNTs, with intensity ratio ID/IG calculated to be 0.92. Field emission scanning electron microscope (FESEM) reveals CNTs are produced on the substrate surface with outer diameter range of 11-44 nm and length of about 0.25 μm. HRTEM further confirmed the graphitic nature of the CNTs obtained. The purity of the nanotubes was analyzed with energy dispersive X-ray (EDX) which showed atomic weight of 98% carbon purity. This paper shows that domestic microwave oven can be used to synthesize CNTs with polymer as the carbon source via plasma catalytic decomposition which was found to be fast, economical and clean technique.

This paper presents results of study on Yttrium iron garnet (YIG) thick film paste using linseed oil as organic binder. YIG nanopowder is mixed with organic vehicle which consists of linseed oil, m-xylene and α-terpineol. Samples with different ratios of compositions are prepared to study the printability and adhesion properties of the paste. Paste samples were then screen printed onto alumina substrate, dried and fired at 300°C. Microscopic images of the samples were observed to determine most suitable ratio for producing YIG paste. Based on the results, YIG paste with 30 wt% ratio showed good adhesion to the substrate as well as having high dielectric property compared to pastes with lower powder ratio.

Highly graphitized nucleophilic group functionalized Multiwall carbon nanotubes are utilized to fabricate PDMS/FMWCNTs nanocomposites with low weight fraction (0.1 wt%). The effect of solvents on dispersion of FMWCNTs is studied. THF shows higher dispersion power in comparison with chloroform. The dielectric constant is measured using impedance analyzer in the range of 106-109 Hz. The result indicate, the dielectric property of FMWCNTs/PDMS nanocomposite could be manipulated with proper mixing techniques and adjustment of curing time.

Detection and quantification of biological and chemical species are critical to many areas of the life sciences and health care, from disease diagnosis to drug screening. Central to detection is the transduction of the signal associated with the sensing event. Advances in nanotechnology have led to the development of the silicon nanowire which is faster, smaller, greener and cheaper. These nanowires have a very narrow diameter similar to that of the chemical and biological species to be sensed making them perfectly suited for biosensing. The top-down fabricated silicon nanowires is used in this work due to its oxide-coated surface and ease of integration with other microelectronic components. Due to the ultra-small output signal of the nanowire, bulky equipments which are often time consuming and expensive are used for reading the signal. This work attempts to build a circuit that can be interfaced with the nanowire to make the signal readable hence the sensor will become portable thereby increasing its utility to being a point-of-care and field-testing device.