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The sensor response of pressure-sensitive conductive elastomers using polymeric materials can be adjusted by altering the type and quantity of fillers used during manufacturing. Another method involves modifying the surface shape of the elastomer. This study investigates the sensor response by altering the surface shape of an electrode using a readily available pressure-sensitive conductive elastomer. By employing an oxygen-free copper electrode with a flat surface (with surface roughness parameters Ra = 0.064 μm and Rz = 0.564 μm) as a baseline, we examined the sensor system's characteristics. Electrodes were fabricated with triangular wave concavo-convex surfaces, featuring tip angles of 60, 90, and 120°. Improved sensor responses were observed with electrodes having tip angles of 60 and 90°. Additionally, even with varying conductive properties of elastomers, the conductance of the elastomer sensor increased similarly when using an electrode with a 90° tip angle. This study demonstrates the potential for expanding the applications of conductive elastomer sensors, highlighting the noteworthy improvement in sensor response and performance achieved by altering the surface shape of electrodes used with commercially available conductive elastomers. [ABSTRACT FROM AUTHOR]

A pixelated bicontrollable metasurface tunable in the complete X band was designed with its meta-atoms comprising yttrium iron garnet (YIG)-patched pixels and conductive rubber (CR)-patched pixels on a metal-backed silicon substrate. Maximum absorptance of a normally incident plane wave greater than 0.99 is achievable and tunability with absorptance exceeding 0.9 is realizable, with the help of an external magnetostatic field and temperature. The YIG-patched pixels provide magnetostatic control modality with sensitivity of 0.04 MHz A − 1 m and the CR-patched pixels provide thermal control modality with sensitivity of 1 MHz K − 1 . The proposed metasurface absorber can be used to improve the performance of weather radar, police speed radar, and direct broadcast television. [ABSTRACT FROM AUTHOR]

Flexible materials that provide an electric, magnetic, or optic response upon deformation or tactile pressure could be important for the development of smart monitors, intelligent textiles, or in the development of robotic skins. In this work we demonstrate the capabilities of a flexible and electrically conductive polymer material that produces an electrical response with any deformation, namely the electrical resistance of the material changes proportionally with the deformation pressure. Furthermore, the material exhibits a memory effect. When compressed beyond the elastic regime, it retains the memory of the plastic deformation by increasing its resistance. The material was obtained by in situ polymerization of semiconducting polyaniline (PANi) in a polyvinyl alcohol/glycerol (PVA/Gly) hydrogel matrix at −17 °C. Upon drying of the hydrogel, an elastomer composite is obtained, with rubber-like characteristics. When compressed/decompressed, the electrical resistance of the material exhibits an unusually long equilibration/relaxation time, proportional with the load applied. These phenomena indicate a complex relaxation and reconfiguration process of the PANi/PVA elastomer matrix, with the shape change of the material due to mechanical stress. [ABSTRACT FROM AUTHOR]

Stretchable and flexible tactile sensors have been extensively investigated for a variety of applications due to their outstanding sensitivity, flexibility, and biocompatibility compared with conventional tactile sensors. However, implementing stretchable multimodal sensors with high performance is still a challenge. In this study, a stretchable multimodal tactile sensor based on conductive rubber composites was fabricated. Because of the pressure-sensitive and temperature-sensitive effects of the conductive rubber composites, the developed sensor can simultaneously measure pressure and temperature, and the sensor presented high sensitivity (0.01171 kPa−1 and 2.46–30.56%/°C) over a wide sensing range (0–110 kPa and 30–90 °C). The sensor also exhibited outstanding performance in terms of processability, stretchability, and repeatability. Furthermore, the fabricated stretchable multimodal tactile sensor did not require complex signal processing or a transmission circuit system. The strategy for stacking and layering conductive rubber composites of this work may supply a new idea for building multifunctional sensor-based electronics. [ABSTRACT FROM AUTHOR]

• Two kinds of sandwich flexible conductive silicon rubber capacitors were prepared by an optimized spraying process. • Equivalent dielectric constant and equivalent capacitance of the capacitor were calculated and analyzed. • The Sprayed conductive silicon rubber capacitance sensors exhibited sensitive to mechanical loads with good repeatability. • Significant improvement of the sensitivity (△C/C0) of the sensor with surface fabric capacitance sensor. With the development of electronic technology, wearable electronic products and electronic skin have become the emerging products in this world. In this study, two kinds of flexible plate capacitors were prepared by an optimized spraying process, whose electrode layers and dielectric layers were conductive silicon rubber and pure PDMS, respectively. The inner surface structure of the capacitors was fabricated with the aids of fabric backup. Initial capacitance and capacitance response of sensors with/without fabric surface structure were calculated and analyzed according to formulae of equivalent dielectric constant of composite dielectric layers and equivalent capacitance of the capacitor. Capacitance responses of the sensors to compressive pressure and tensile strain loads were further tested. In addition, the effect of spraying parameters, including spraying distance, plate area and resistance of the CSR with loads were evaluated on the response. The sprayed flexible capacitors were finally demonstrated its potential application in sensing field, such as water dropping, feet lifting and walking. Results indicate that the surface fabric structure of flexible sensors will improve its stability and sensitivity, which assure the sensors of a prospect of motion sensor. [ABSTRACT FROM AUTHOR]

• Evaluating of conductive rubber and conductive ink as a foil pressure-resistance transducer. • Direct comparison of both materials on a robotized measuring workplace. • Both materials proved their ability to act as a transducer within a limited range of applied pressure. • Best results were obtained for the thinnest layer of conductive ink. The article presents end evaluates foil transducers, namely conductive rubber and conductive ink, and their use in the pressure distribution measurement system Plantograf. The ability of both materials to act as transducer between pressure and electrical quantities is assessed by means of measurement on a robotized workspace; two electrode types and various ink layer thicknesses are studied. Basing on the measurements, we present graphically the dependency of the electrical resistance of the materials on the applied pressure. Although both materials proved their ability to act as a transducer in a planar sensor, they both exhibit some limitations. In case of rubber it is limited pressure range up to ca. 1 400 kPa and significant hysteresis of the material. The main limiting factor with conductive ink is its poor adherence to the electrodes, which poses important problem for its practical use, although this material evinces better transfer characteristics, particularly in the configuration with 7 μm ink layer and LD type electrode. [ABSTRACT FROM AUTHOR]

Abstract: Electrical impedance of plants is related to condition of the plant's cell tissue. In existing works, the impedance has been utilized for understanding the condition of the plant. There are three kinds of electrode for measuring the impedance: a needle electrode, a metallic foil electrode, and a conductive gel electrode. However, these electrodes have problems. The needle electrode injures the plants. The metallic foil electrode does not stably contact to the plant because the plants has curve and convexo–concave surface. The conductive gel electrode including NaCl blasts the plants. We proposed a conductive unvulcanized rubber electrode for measuring the electrical impedance of the carrots. Characteristics of the conductive unvulcanized rubber electrode were soft, deformable, and self‐adhesive. Thus, the electrode was noninvasive and did not damage to the carrots. In experiments, we showed that the conductive unvulcanized rubber electrode could be utilized for measuring electrical impedance of a carrot for 912 h. Moreover, we observed that the contact area of the electrode was larger than the contact area of a conductive adhesive tape electrode. [ABSTRACT FROM AUTHOR]

Sulphur-vulcanised epoxidised natural rubber-polyaniline dodecylbenzenesulfonate (ENR-PAni.DBSA) blends with useful electrical conductivities (up to 10-1 S/cm) and adjustable electrostrictive behaviour were successfully produced via a thermomechanical mixing method. A reasonably high level of compatibility between ENR and PAni.DBSA was observed from both Fourier transform infrared spectroscopy and transmission electron microscopy studies. As found from both electrostrictive strain (Sz) tests, ENR-PAni.DBSA blends with 10.0-30.0 wt% of PAni.DBSA content possessed the best electrostrictive response (Sz up to 12.25%) with applied electric field strengths up to 50 V/mm. Apart from this, blends with very low and very high PAni.DBSA contents (i.e.⩽5.0 wt% and ⩾40.0 wt%) had much poorer electrostrictive responses under the same level of applied electrical field, which is due to their lower dielectric properties and higher level of phase separation between ENR and PAni.DBSA. [ABSTRACT FROM AUTHOR]

Peroxide-vulcanised NBR-PAni.DBSA blends with useful electrical conductivities (up to 10-1 S.cm-1) were prepared and their electrostrictive behaviours under certain levels of applied electric field were also successfully assessed. A reasonable high level of compatibility between NBR andPAni.DBSA was observedfrom both FT-IR spectroscopy and TEM microscopy studies. As found from both electrostrictive strain (S) tests, NBR- PAni.DBSA blends with 10.0 - 30.0 wt % of PAni.DBSA content possessed the best electrostrictive response (Sz up to 11.8%) with applied electricalfield strengths up to 50 V/µm. Besides this, blends consisting of very low and very high PAni.DBSA contents (i.e. ≤ 5.0 wt % and ≥ 40.0 wt %) possessed poorer electrostrictive responses under the same level of applied electricalfield due to their lower dielectricalproperties and higher phase separation problem between the two major constituent polymers. [ABSTRACT FROM AUTHOR]

This article presents a thermally tunable Fano resonator obtained by asymmetrically coupling a conductive rubber-based H-shaped split ring resonator (SRR) and a copper C-shaped SRR coated on a Teflon fiberglass slab substrate. Thermal tunability of the Fano resonance is provided by the temperature-sensitive resistance property of the conductive rubber. The thermal tunability of the Fano resonance obtained from the proposed resonator structure is demonstrated by both simulation and experimental results. This study provides a novel tunable approach for designing dynamical electromagnetic modulation devices. [ABSTRACT FROM AUTHOR]

As it has outstanding electrical and mechanical properties, like high conductivity, durability, and flexibility, graphene may be an interesting material also for conformal and wearable antennas. Whereas mono-atomic graphene layers have been proven to perform inadequately at microwave frequencies, in this article the performance of multilayered graphene-based sheets (GBS) fabricated onto a polymer substrate is assessed when used as flexible planar and conformal antennas. This is accomplished through studying a simple microstrip antenna topology. Challenges related to the fabrication process of these antennas are discussed, for example adhesion issues and the occurrence of air gaps on the substrate layer. The graphene-based technology is compared to a classical technology involving copper as metal. Bending of the antennas is also discussed. The main conclusion is that multilayered graphene does perform adequately as conductor in antennas at microwave frequencies, with the possibility of providing a slightly higher gain than copper. [ABSTRACT FROM AUTHOR]

A flexible microstrip grid array antenna (MGAA) fabricated by printing the patch and the ground plane using a 0.25 -mm -thick conductive rubber layer onto a 1.9 mm thick Polydimethylsiloxane (PDMS) substrate layer is presented in this article. The proposed antenna was designed to operate at 14 GHz frequency band. It is composed of 24 radiating elements to achieve a high gain and compact size characteristics. The measurement results shows that the antenna exhibits wideband characteristics in return loss ( S11) covered from 12 to 18 GHz and it can works at bending state without sacrificing the performance. The measured radiation pattern results also present good agreement with the simulated results. All the criteria of this proposed antenna make it as a suitable candidate to be applied for future flexible and conformal-5G mobile communication applications. [ABSTRACT FROM AUTHOR]

This paper presents the design and related applications of a thermally tunable band-stop filter employing conductive rubber that incorporates electrically conductive particles. The relationship between the environmental temperature and the volume resistivity of conductive rubber materials was experimentally established. The experimental results demonstrated that the conductive rubber has a temperature-sensitive resistance property. The conductive rubber material was employed in the design of a C-shaped split-ring resonator (SRR) structure. The influence of environmental temperature on the electromagnetic properties of the SRR structure was analysed using a numerical simulation and experimental testing. The results demonstrated that the design of thermally tunable metamaterials was possible. As such, an H-shaped conductive rubber SRR was employed in the design of a novel thermally tunable band-stop filter. The results of a numerical simulation and experimental testing verified its band-stop characteristic, and demonstrated that the filtering performance of the H-shaped conductive rubber SRR can be controlled by the environmental temperature. Lastly, by comparison of the effective dielectric properties of the two types of SRRs, it demonstrates the effectiveness of conductive rubber and their temperature-controllable band-stop characteristics. [ABSTRACT FROM AUTHOR]

Method, formulation and mechanical load variation on electrical conductivity of natural rubber composites filled with multi-wall carbon nanotube and carbon black have been investigated. These nanometer-scale fillers were used due to their good dispersion in the rubber matrix together with their good electrical conductivity. Samples were prepared using five conventional methods involving internal and open-mill mixers, and molding using hot compression machine. Desirable high conductivity and well defined flexure was found best from compounding employing internal mixer which rendered better control in the mixing of chemicals. Two formulations of carbon black were studied: Ketjen Black and Vulcan Black; mixture of the two yielded better conductivity and response to loads than that of Vulcan Black alone, and that the higher the filler content, the better. Conductivity responses to mechanical loading were analyzed at three loading conditions: compression, shear, and combinations of the two. Conductivity of the composite subjected to pure compressive stress and that subjected to loading at different angles similarly behaved nonlinearly; increasing with the angle with respect to normal strain. With respect to shear strain, conductivity increases with decreasing loading angle. [ABSTRACT FROM AUTHOR]

An eartip made of conductive rubber that also realizes biopotential electrodes is proposed for a daily-use earphone-based eye gesture input interface. Several prototypes, each with three electrodes to capture electrooculogram (EOG), are implemented on earphones and examined. Experiments with one subject over a 10-day period reveal that all prototypes capture EOG similarly but they differ as regards stability of the baseline and the presence of motion artifacts. Another experiment conducted on a simple eye-controlled application with six subjects shows that the proposed prototype minimizes motion artifacts and offers good performance. Artifacts induced by daily motion while wearing the proposed electrode and eye gesture performance are also measured, and we discuss how to deal with them. We conclude that conductive rubber with mixed Ag filler is the most suitable setup in our experiment. [ABSTRACT FROM AUTHOR]

Traditional capacitive tactile sensor sheets usually have a three-layered structure, with a dielectric layer sandwiched by two electrode layers. Each electrode layer has a number of parallel ribbon-like electrodes. The electrodes on the two electrode layers are oriented orthogonally and each crossing point of the two perpendicular electrode arrays makes up a capacitive sensor cell on the sheet. It is well known that compatibility between measuring precision and resolution is difficult, since decreasing the width of the electrodes is required to obtain a high resolution, however, this may lead to reduction of the area of the sensor cells, and as a result, lead to a low Signal/Noise (S/N) ratio. To overcome this problem, a new multilayered structure and related calculation procedure are proposed. This new structure stacks two or more sensor sheets with shifts in position. Both a high precision and a high resolution can be obtained by combining the signals of the stacked sensor sheets. Trial production was made and the effect was confirmed. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to provide a thin tactile force sensor array based on conductive rubber and to offer descriptions of the sensor design, fabrication and test. Design/methodology/approach – The sensor array consists of a sandwich structure. Sensing elements are distributed discretely in the sensor. Each sensing element has two electrodes and a piece of conductive rubber with piezoresistive property. The electrodes, as well as the conductive trace for signal transmission, are printed on the substrate layer by the screen printing technique. A scanning circuit based on zero potential method and an experimental set-up based on balance to characterize the sensor array are designed and implemented in the test of the sensor array. Findings – Experimental results verify the validity of the sensor array in measuring the vertical tactile force between the sensing elements and the object. Research limitations/implications – In this paper, all the sensors are tested without calibration procedures and the procedure of the dynamic test is implemented by manual operation. Practical implications – The sensor array could be applied to measure the plantar force for gait detection in clinical applications. Originality/value – The paper presents a tactile force sensor array with discrete sensing elements to essentially restrict the cross-talk among sensing elements. This paper will provide many practical details that can help others in the field. [ABSTRACT FROM AUTHOR]

Ternary composites of natural rubber filled with particulate carbonaceous and metal fillers were developed for electro-mechanical sensing purposes, while maintaining good elasticity and loading capability. The effects of filler type and composition on electrical and mechanical properties of binary and ternary conductive composites have been examined. The typical mechanical-compounding and molding processes for rubbers were used for this study. As observed, the binary composite containing 50 phr carbon black in natural rubber was the superior conductive composite for a pressure sensor based on its balance of compression set and electrical conductivity. At the same total filler content, a third metal component filler decreases the electrical conductivity of the binary composites. In addition, the third component of metal fillers deteriorates the compression set of the composites. [ABSTRACT FROM AUTHOR]

• The conductive rubber content more than 1.28 vol.% could significantly improve electrical conductivity. • The composites with 1.28 vol.% rubber fibres at w/b ratio of 0.38 express higher sensitivity and repeatability. • Three piezoresistivity mechanisms were proposed for the conductive rubber/cement composite. • Piezoresistivity fluctuated not only due to more rubber content, but also too much water content. • Compressive strength decreased with increase of rubber content due to the micro cracks in the rubber/cement boundaries. Piezoresistive-based cementitious composites have unique advantages compared with other sensors for structural health monitoring. A novel cement-based sensor incorporating conductive rubber was explored in this study, including its raw materials, manufacturing process, electrical conductivity, self-sensing efficiency, repeatability and compressive strength. Different water to binder (w/b) ratios of composites and loading stress magnitudes were also investigated. The results show that the conductive rubber fibres had capacity to improve the electrical conductivity of cementitious composite, with percolation threshold approximately from 60–100 rubber fibres (0.96–1.6 vol.% to specimen). The higher w/b ratio, the lower resistivity and the more inconspicuous percolation the composite was. Furthermore, the composites at w/b ratio of 0.38 were provided with best piezoresistivity, whose fractional changes of resistivity reached 25% under stress magnitude of 10 MPa when reinforced by 80 rubber fibres (1.28 vol.%). The sensitive coefficient proposed could describe piezoresistive sensitivity in different stress magnitudes, because of the non-linear resistivity changes with increased stress amplitude. As for the mechanical properties, satisfactory compressive strength of 36 MPa was obtained for the composite filled with 80 rubber fibres (1.28 vol.%) at w/b ratio of 0.38. Therefore, the conductive rubber embedded cementitious composites have great application potential as new cement-based sensors for concrete structural health and pavement traffic monitoring. [ABSTRACT FROM AUTHOR]