Fabrication and Investigation of Deformable Rubber-Carbon Nanotube-Glue Gel-Based Impedimetric and Capacitive Tactile Sensors for Pressure and Displacement Measurements.

Carbon nanotube-glue composite gel-based surface-type elastic sensors with a cylindrical shape deformable (flexible) metallic body were fabricated for tactile pressure and compressive displacement sensing. The fabrication of the sensors was performed using the rubbing-in technique. The effect of the pressure and the compressive displacement on the capacitance and the impedance of the sensors were investigated at various frequencies (in the range of 1 kHz to 200 kHz). It was found that under the effect of pressure from 0 to 9 g/cm2, the capacitance increased by 1.86 and 1.78 times, while the impedance decreased by 1.84 and 1.71 times at the frequencies of 1 kHz to 200 kHz, respectively. The effect of displacement on the impedance and the capacitance of the device was also investigated at various frequencies from 1 kHz to 200 kHz. The results showed that under the effect of compressive displacement up to 25 µm, the impedance of the sensors decreased on average by 1.19 times, while the capacitance increased by 1.09 times, accordingly. The frequency response of the displacement sensor showed that it matched with the low-pass filter. The obtained results are explained based on changes in the shape and geometrical parameters of the cylindrical-shaped conductive body. These results have also been explained on the basis of the distance between the conductive plates of the capacitive sensors during compression, which takes place under the effect of applied pressure or displacement. Moreover, the design of the sensors is simple and easy to fabricate, and their use is also earthy. The fabricated sensors have great potential for commercialization.

Orange Dye and Silicone Glue Composite Gel-Based Optimized Impedimetric and Capacitive Surface-Type Proximity Sensors.

Optimized surface-type impedimetric and capacitive proximity sensors have been fabricated on paper substrates by using rubbing-in technology. The orange dye (OD) and silicone glue (SG) composite-gel films were deposited on the zig-zag gap between two aluminum electrodes fixed on a paper (dielectric) substrate. The effect of proximity of various objects (receivers) on the impedance and the capacitance of the sensors was investigated. These objects were semi-cylindrical aluminum (metallic) foil, a cylindrical plastic tube filled with water, a kopeck-shaped plastic tube filled with carbon nanotubes and a human finger. The mechanism of sensing was based on the change in impedance and/or the capacitance of the sensors with variation of proximity between the surfaces of the sensor and the object. On decreasing proximity, the impedance of the sensors increased while the capacitance decreased. The impedimetric proximity sensitivities of CNT, water, metal-based receivers and the finger were up to 60 × 103 Ω/mm, 35 × 103 Ω/mm, 44 × 103 Ω/mm and 6.2 × 103 Ω/mm, respectively, while their capacitive sensitivities were -19.0 × 10-2 pF/mm, -16.0 × 10-2 pF/mm, -16.4 × 10-2 pF/mm and -1.8 × 10-2 pF/mm. If needed for practical application, the sensors can be built in to the Wheatstone bridge, which can also increase the sensitivity of the measurement. Moreover, the sensor's materials are low cost, while the fabrication technique is easy and ecologically friendly. The sensor can also be used for demonstrative purposes in school and college laboratories.

Fabrication and Investigation of Graphite-Flake-Composite-Based Non-Invasive Flex Multi-Functional Force, Acceleration, and Thermal Sensor.

This work examines the physics of a non-invasive multi-functional elastic thin-film graphite flake-isoprene sulfone composite sensor. The strain design and electrical characterization of the stretching force, acceleration, and temperature were performed. The rub-in technique was used to fabricate graphite flakes and isoprene sulfone into sensors, which were then analyzed for their morphology using methods such as SEM, AFM, X-ray diffraction, and Fourier transform infrared spectroscopy to examine the device's surface and structure. Sensor impedance was measured from DC to 200 kHz at up to 20 gf, 20 m/s2, and 26-60 °C. Sensor resistance and impedance to stretching force and acceleration at DC and 200 Hz rose 2.4- and 2.6-fold and 2.01- and 2.06-fold, respectively. Temperature-measuring devices demonstrated 2.65- and 2.8-fold decreases in resistance and impedance at DC and 200 kHz, respectively. First, altering the graphite flake composite particle spacing may modify electronic parameters in the suggested multi-functional sensors under stress and acceleration. Second, the temperature impacts particle and isoprene sulfone properties. Due to their fabrication using an inexpensive deposition technique, these devices are environmentally friendly, are simple to build, and may be used in university research in international poverty-line nations. In scientific laboratories, such devices can be used to teach students how various materials respond to varying environmental circumstances. They may also monitor individuals undergoing physiotherapy and vibrating surfaces in a controlled setting to prevent public health risks.

Shockproof Deformable Infrared Radiation Sensors Based on a Polymeric Rubber and Organic Semiconductor H2Pc-CNT Composite.

Polymeric rubber and organic semiconductor H2Pc-CNT-composite-based surface- and sandwich-type shockproof deformable infrared radiation (IR) sensors were fabricated using a rubbing-in technique. CNT and CNT-H2Pc (30:70 wt.%) composite layers were deposited on a polymeric rubber substrate as electrodes and active layers, respectively. Under the effect of IR irradiation (0 to 3700 W/m2), the resistance and the impedance of the surface-type sensors decreased up to 1.49 and 1.36 times, respectively. In the same conditions, the resistance and the impedance of the sandwich-type sensors decreased up to 1.46 and 1.35 times, respectively. The temperature coefficients of resistance (TCR) of the surface- and sandwich-type sensors are 1.2 and 1.1, respectively. The novel ratio of the H2Pc-CNT composite ingredients and comparably high value of the TCR make the devices attractive for bolometric applications meant to measure the intensity of infrared radiation. Moreover, given their easy fabrication and low-cost materials, the fabricated devices have great potential for commercialization.

Effect of Vibrations, Displacement, Pressure, Temperature and Humidity on the Resistance and Impedance of the Shockproof Resistors Based on Rubber and Jelly (NiPc-CNT-Oil) Composites.

Here, we present the design, fabrication and characterization of shockproof rubber-jelly (NiPc-CNT-oil) composite-based resistors. To fabricate the resistors, gels of CNT and NiPc with edible oil were prepared and deposited on a flexible rubber substrate using rubbing-in technique. The devices' resistance and impedance were investigated under the effect of pressure, displacement, humidity, temperature and mechanical vibrations. The resistance and the impedance decreased, on average, by 1.08 times under the effect of pressure (up to 850 gf/cm2) and by 1.04 times under the effect of displacement (up to 50 µm). Accordingly, upon increasing the humidity from 60% to 90% RH, the resistance and impedance decreased by up to 1.04 times, while upon increasing the temperature from 25 °C to 43 °C, the resistance and impedances also decreased by up to 1.05 times. Moreover, under the effect of vibration, a decrease in resistance and impedance, by up to 1.03 times, was observed. The investigated samples can potentially be used as prototypes for the development of shockproof jelly electronic-based devices in particular resistors. The technological achievement in the fabrication of these devices is the use of edible organic oil, which allows for the fabrication of uniform jelly films of organic materials that cannot be realized simply by mixing "dry" ingredients. Especially, we highlight that edible organic oil is environmentally friendly, unlike some other inorganic oils that are used in practice.

Effect of Humidity and Temperature on the Impedances and Voltage of Al/Gr-Jelly/Cu-Rubber Composite-Based Flexible Electrochemical Sensors.

Here we present the fabrication of graphene and jelly (superabsorbent polymer) electrolyte composite-based shockproof flexible electrochemical sensors (Al/Gr-Jelly/Cu) and their properties under the effect of humidity and temperature. A layer of graphene mixed in jelly electrolyte was drop-casted onto porous rubber substrates between preliminary fixed aluminum (Al) and copper (Cu) electrodes followed by rubbing-in. It was observed that the graphene and jelly mixture was mechanically soft and flexible, similar to jelly. Electrically, this mixture (graphene and jelly) behaved as a flexible electrolyte. It was observed that under the effect of humidity ranging from 47 to 98%, the impedances of the sensors decreased by 2.0 times on average. Under the effect of temperatures ranging from 21 to 41 °C the impedances decreased by 2.4 times. The average temperature coefficient of impedances was equal to -0.03 °C-1. The electrochemical voltage generated by the flexible jelly electrolyte sensors was also investigated. It was found that the initial open-circuit voltages were equal to 201 mV and increased slightly, by 5-10% under the effect of humidity and temperature as well. The short-circuit currents under the effect of humidity and temperature increased by 2-3 times. The Al/Gr-Jelly/Cu electrochemical sensors may be used as prototypes for the development of the jelly electronic-based devices.

Ultraviolet and Infrared Irradiations Sensing of Gel-Orange Dye Composite-Based Flexible Electrochemical Cells.

The flexible and shockproof rubber-based Al/OD-Gel/Cu electrochemical cell was designed, fabricated, and investigated for the detection of IR and UV irradiations. For this purpose, the transparent gel-orange dye composite was deposited on the porous rubber substrate between aluminum and copper electrodes. It was observed that the gel-orange dye composite was mechanically like a gel: soft and flexible. Electrically, this composite (gel-orange dye) forms a flexible electrolyte. It was found that the impedance of the samples under the effect of infrared irradiation decreased by 2.02 to 2.19 times on changing frequency from 100 Hz to 200 kHz. Accordingly, under the effect of ultraviolet irradiation, the impedance of the samples decreased by 1.23 to 1.45 times on increasing frequency from 100 Hz to 200 kHz. Under the effect of infrared irradiation up to 4000 W/m2, the cell's open-circuit voltage increased by 1.59 times. The cell's open-circuit voltage also increased by 1.06 times under the effect of ultraviolet irradiation up to 200 uW/cm2. The mechanism of the absorption of the infrared and ultraviolet irradiations by the OD-Gel composite has been discussed in detail. The fabricated flexible rubber substrate-based Al/OD-Gel/Cu electrochemical cells can be used as a prototype for the development of gel electronics-based devices.

An ensemble framework based on Deep CNNs architecture for glaucoma classification using fundus photography.

Glaucoma is a chronic ocular degenerative disease that can cause blindness if left untreated in its early stages. Deep Convolutional Neural Networks (Deep CNNs) and its variants have provided superior performance in glaucoma classification, segmentation, and detection. In this paper, we propose a two-staged glaucoma classification scheme based on Deep CNN architectures. In stage one, four different ImageNet pre-trained Deep CNN architectures, i.e., AlexNet, InceptionV3, InceptionResNetV2, and NasNet-Large are used and it is observed that NasNet-Large architecture provides superior performance in terms of sensitivity (99.1%), specificity (99.4%), accuracy (99.3%), and area under the receiver operating characteristic curve (97.8%) metrics. A detailed performance comparison is also presented among these on public datasets, i.e., ACRIMA, ORIGA-Light, and RIM-ONE as well as locally available datasets, i.e., AFIO, and HMC. In the second stage, we propose an ensemble classifier with two novel ensembling techniques, i.e., accuracy based weighted voting, and accuracy/score based weighted averaging to further improve the glaucoma classification results. It is shown that ensemble with accuracy/score based scheme improves the accuracy (99.5%) for diverse databases. As an outcome of this study, it is presented that the NasNet-Large architecture is a feasible option in terms of its performance as a single classifier while ensemble classifier further improves the generalized performance for automatic glaucoma classification.

A Novel Poly-N-Epoxy Propyl Carbazole Based Memory Device.

Generally, polymer-based memory devices store information in a manner distinct from that of silicon-based memory devices. Conventional silicon memory devices store charges as either zero or one for digital information, whereas most polymers store charges by the switching of electrical resistance. For the first time, this study reports that the novel conducting polymer Poly-N-Epoxy-Propyl Carbazole (PEPC) can offer effective memory storage behavior. In the current research, the electrical characterization of a single layer memory device (metal/polymer/metal) using PEPC, with or without doping of charge transfer complexes 7,7,8,8-tetra-cyanoquino-dimethane (TCNQ), was investigated. From the current-voltage characteristics, it was found that PEPC shows memory switching effects in both cases (with or without the TCNQ complex). However, in the presence of TCNQ, the PEPC performs faster memory switching at relatively lower voltage and, therefore, a higher ON and OFF ratio (ION/IOFF ~ 100) was observed. The outcome of this study may help to further understand the memory switching effects of conducting polymer.

A novel and stable way for energy harvesting from Bi2Te3Se alloy based semitransparent photo-thermoelectric module.

In this research, due to the present pandemic of COVID-19, we are proposing a stable and fixed semitransparent photo-thermoelectric cell (PTEC) module for green energy harvesting. This module is based on the alloy of Bismuth Telluride Selenide (Bi2Te3Se), designed in a press tablet form and characterized under solar energy. Here, both aspects of solar energy i.e., light and heat are utilized for both energy production and water heating. The semitransparent PTEC converts heat energy directly to electrical energy due to the gradient of temperature between two electrodes (top and bottom) of thermoelectric cells. The PTEC is 25% transparent, which can be varied according to the necessity of the utilizer. The X-ray diffraction of material and electric characterization of module i.e., open-circuited voltage (VOC) and Seebeck coefficient were performed. The experimental observations disclose that in the proposed PTEC module with an increment in the average temperature (TAvg) from 34 to 60 °C, results in the rise of VOC âˆ¼ 2.4 times. However, by modifying the size of heat-absorbing top electrode and by increasing the temperature gradient through the addition of water coolant under the bottom electrode, an uplift in the champion device results in as increment of VOC ∼5.5 times and Seebeck coefficient obtained was -250 µV/0C, respectively. Results show that not only the selection of material but also the external modifications in the device highly effective the power efficiency of the devices. The proposed modules can generate electric power from light and utilize the penetrating sunlight inside the room and for the heating of the water which also acts as a coolant. These semitransparent thermoelectric cells can be built-in within windows and roofs of buildings and can potentially contribute to green energy harvesting, in situations where movement is restricted locally or globally.

Decade of 2D-materials-based RRAM devices: a review.

Two dimensional (2D) materials have offered unique electrical, chemical, mechanical and physical properties over the past decade owing to their ultrathin, flexible, and multilayer structure. These layered materials are being used in numerous electronic devices for various applications, and this review will specifically focus on the resistive random access memories (RRAMs) based on 2D materials and their nanocomposites. This study presents the device structures, conduction mechanisms, resistive switching properties, fabrication technologies, challenges and future aspects of 2D-materials-based RRAMs. Graphene, derivatives of graphene and MoS2 have been the major contributors among 2D materials for the application of RRAMs; however, other members of this family such as hBN, MoSe2, WS2 and WSe2 have also been inspected more recently as the functional materials of nonvolatile RRAM devices. Conduction in these devices is usually dominated by either the penetration of metallic ions or migration of intrinsic species. Most prominent advantages offered by RRAM devices based on 2D materials include fast switching speed (<10 ns), less power losses (10 pJ), lower threshold voltage (<1 V) long retention time (>10 years), high electrical endurance (>108 voltage cycles) and extended mechanical robustness (500 bending cycles). Resistive switching properties of 2D materials have been further enhanced by blending them with metallic nanoparticles, organic polymers and inorganic semiconductors in various forms.

A novel and stable ultraviolet and infrared intensity sensor in impedance/capacitance modes fabricated from degraded CH3NH3PbI3-xClx perovskite materials.

The present situation of COVID-19 diverted our focus towards utilizing the degraded solar cells for sensor application, this will help in global energy harvesting. So, here is our successful effort to reuse already degraded solar cells as ultraviolet (UV) and infrared (IR) sensor. The spin-coated perovskite (CH3NH3PbI3-XClX) has been already tested for visible light spectrum, as an extension to that now it is utilized as UV and IR intensity sensors to cover the whole spectrum. The employed CH3NH3PbI3-XClX material was used after its efficiency loss has been reached to a saturation point in photovoltaic devices. Each deposited layer was investigated from UV to the IR absorption spectrum for deepening study through UV-vis spectroscopy. In the sandwiched architecture possessing FTO/PEDOT: PSS/Perovskite/PC61BM/CdS/Au symmetry, the perovskite film has been employed as an absorbent layer, however, other layers participation also plays a key role. The resultant device yielded very good sensing performance because of the enhanced excitons generation which is attributed to the precise selection of the interfacial materials, e.g. CdS and PC61BM as an ETM and PEDOT: PSS as HTM. The impedance and capacitance of the devices within 0.01-200 kHz under varied UV and IR illumination intensities were investigated. Measurements showed that as the intensity of the light increased i.e., UV (0-200 W/m2) and IR (0-5800 W/m2), impedance decreased while capacitance increased. The current results are attributed to the increase in the concentration of charges i.e., electron-hole pairs generation depending on the built-in capacitance and frequency of the charges.

Fabrication of flexible conductive films by rubbing in technology for application in elastic thermo-electric cells.

This method solves the problem of fabrication of flexible elastic conductive thin film samples for thermoelectric applications. For this purpose, rubbing in technology at room temperature condition has been used which is simple, economical and reliable. As a result, elastic thermo-electric cells have been fabricated that can be used for low power applications and for measurement of the gradient of temperature in industry, medicine and in instrumentation as well. The elastic nature of the thermo-electric cells allows us to place the "hot" and "cold" points of the thermo-electric cells in different planes that make these thermo-electric cells useful for different kind of applications without limitation to place them in a line or in a plane.

Effective management of combined renewable energy resources in Tajikistan.

Water is needed mostly in summer time for irrigation and in winter time for generation of electric power. This results in conflicts between downstream countries that utilize water mostly for irrigation and those upstream countries, which use water for generation of electric power. At present Uzbekistan is blocking railway connection that is going to Tajikistan to interfere to transportation of the equipment and materials for construction of Rogun hydropower plant. In order to avoid conflicts between Tajikistan and Uzbekistan a number of measures for the utilization of water resources of the trans-boundary Rivers Amu-Darya and Sir-Darya are discussed. In addition, utilization of water with the supplement of wind and solar energy projects for proper and efficient management of water resources in Central Asia; export-import exchanges of electric energy in summer and winter time between neighboring countries; development of small hydropower project, modern irrigation system in main water consuming countries and large water reservoir hydropower projects for control of water resources for hydropower and irrigation are also discussed. It is also concluded that an effective management of water resources can be achieved by signing Water treaty between upstream and downstream countries, first of all between Tajikistan and Uzbekistan. In this paper management of water as renewable energy resource in Tajikistan and Central Asian Republics are presented.

A humidity sensing organic-inorganic composite for environmental monitoring.

In this paper, we present the effect of varying humidity levels on the electrical parameters and the multi frequency response of the electrical parameters of an organic-inorganic composite (PEPC+NiPc+Cu2O)-based humidity sensor. Silver thin films (thickness ~200 nm) were primarily deposited on plasma cleaned glass substrates by the physical vapor deposition (PVD) technique. A pair of rectangular silver electrodes was formed by patterning silver film through standard optical lithography technique. An active layer of organic-inorganic composite for humidity sensing was later spun coated to cover the separation between the silver electrodes. The electrical characterization of the sensor was performed as a function of relative humidity levels and frequency of the AC input signal. The sensor showed reversible changes in its capacitance with variations in humidity level. The maximum sensitivity ~31.6 pF/%RH at 100 Hz in capacitive mode of operation has been attained. The aim of this study was to increase the sensitivity of the previously reported humidity sensors using PEPC and NiPc, which has been successfully achieved.