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Purpose The purpose of this study is to investigate the utility of carbon black containing coating formulations that are conventionally used for pigment printing of textiles in fabricating electrically heated fabrics. Design/methodology/approach Specifically, electrical and thermal characterisation of the coating system was carried out to establish the feasibility of the system for use in the manufacturing of flexible heating elements on textile substrates. The coating formulations were applied via a simple padding technique followed by stitching the electrodes using a conductive yarn. Findings The heating elements of different sizes thus produced showed Ohmic behaviour as a resistor and attained a targeted temperature difference of up to 40°C within the applied voltage range. A prototype heater was also produced, and thermography results showed uniform heating and cooling of the heater that was incorporated into a jacket. Originality/value The proposed method is envisaged to be very practical for the realisation of completely textile-based heating elements of different shapes and sizes. Furthermore, the proposed manufacturing method can be used to convert conventional ready-made articles of clothing into heated textiles for various applications.

Due to the inherent environmental and health toxicities associated with lead, the use of environmental friendly lead-free solder materials has become an unavoidable trend in the electronic packaging industry. Sn-58Bi alloy is gaining attention for its good material properties such as low melting point, reliability and high tensile strength. The presence of the bismuth-rich phase increases the brittleness of Sn-58Bi alloy. The purpose of this study is to suppress the brittleness of Sn-58Bi alloy by the addition of different wt% (0, 10, 20, 30) of Sn powder. The powder metallurgy method was used to prepare the samples. Scanning electron microscopy and energy-dispersive X-ray analysis were done to study the structural properties and a tensile test was done by a universal tensile machine to study the mechanical properties. The results reveal that the Sn particles partially dissolved in the Sn-58Bi solder matrix. The dissolution of Sn particles significantly improved the mechanical strength by 30%, suppressed the brittleness and improved the strain value by 1.3 times.

Purpose Among various metal oxide nano particles, MgO NPs and ZnO nanoparticles (NPs) in particular are gaining increasing attention due to their multifunctional characteristics, low cost and compatibility with textile materials. Each type of nanoparticle excels over others in certain properties. As such, it is often crucial to carry out comparative studies of NPs to identify the one showing higher efficiency/output for particular applications of textile products. Design/methodology/approach In the investigation reported in this paper, ZnO NPs and MgO NPs were synthesised via sol-gel technique and characterised. For comparative analysis, the synthesised NPs were evaluated for multiple properties using standard procedures before and after being applied on cotton fabrics by a dip-pad-dry-cure method. Findings XRD and FTIR analyses confirmed the successful synthesis of ZnO and MgO NPs. Homogeneous formation of desired NPs and their dense and uniform deposition on the cotton fibre surface were observed using SEM. ZnO NPs and MgO NPs coatings on cotton were observed to significantly enhance self-cleaning/stain removal properties achieving Grade 5 and Grade 4 categories, respectively. In terms of ultraviolet (UV) protection, ZnO or MgO NP coated fabrics showed UPF values of greater than 50, i.e. excellent in blocking UV rays. MgO NPs exhibited 20% cleaning efficiency in treating reactive dye wastewater against ZnO NPs which were 4% efficient in the same treatment, so MgO was more suitable for such type of treatments at low cost. Both NPs were able to impart multifunctionality to cotton fabrics as per requirement of the end products. However, ZnO NPs were better for stain removal from the fabrics while MgO NPs were appropriate for UV blocking. Originality/value It was therefore clear that multifunctional textile products could be developed by employing a single type of cost effective and efficient nano particles.

Purpose Pretreatment of fabric with a number of chemicals and auxiliaries is a prerequisite for inkjet printing. Owing to the rapidly increasing use of inkjet printing for textile fabrics, the study of the effects of process variables on various characteristics of the resulting print has drawn considerable interest recently. The purpose of this paper is to study the effects of different variables associated with the inkjet printing process on the quality of the resulting print. Specifically, the effects of chemicals and auxiliaries used in the pretreatment of the fabric prior to printing and factors such as steaming time were studies. Design/methodology/approach In the present study, which forms a part of a larger study by the authors, the influence of the nature of thickener, the amounts of thickener, urea and alkali, pH of the pretreatment liquor and the duration of steaming on ink penetration into the printed fabrics and the ink spreading across the fabrics was studied. The nature of ink penetration and ink spreading are known to have pronounced effects on the quality and, in turn, the overall appearance of the resulting print. A set of experiments based on a blocked 25–1 fractional factorial design with four centre points were conducted to evaluate the role of the aforementioned five variables. Ink penetration was quantified on the basis of the principles of Kebulka-Munk theory while ink spreading was analysed by image analysis. Findings Detailed statistical analyses of the experimental data obtained show that different thickeners perform differently and can have a marked influence on ink penetration and ink spreading. In the case of polyacrylic acid-based thickener, changing the levels of the factors has a marked effect on ink penetration and in-turn on ink spreading. In the case of polyacrylamide (PAM)-based thickener, on the other hand, the effect of changing the levels of various factors on the ink penetration and ink spreading is considerably less pronounced. In addition, PAM treated samples exhibited better performance in terms of ink penetration and spreading. Originality/value This study provides useful information for textile printers and highlights the importance of selecting the right type of thickener to make the printing process and the quality of the resulting print more predictable and controllable.

peer-reviewed Traditionally, symmetric accelerating beam (SAB) generation requires bulky optical components, which hinder the miniaturization of optical systems. Recently, metasurfaces, which are composed of sub-wavelength features, have provided a captivating boulevard for the realization of ultra-thin and flat optical devices. Therefore, for the first time, we design and simulate all-dielectric metasurfaces based on an optical caustic approach to generate highly efficient SABs by tailoring the phase of an incident wave. The designed metasurface utilizes spatial distribution of optimized Nb2O5 nano-rods on SiO2 substrate to perform the phase modulation. In contrast with conventional accelerating beams, the generated SABs can follow any predefined propagation trajectory with unique features, such as symmetric intensity profile, autofocusing, and thin needle-like structure in their intensity profile. In addition to this, these beams have also shown the ability to avoid obstacles, placed in the direction of propagation of main lobes. We believe that these beams can be useful in applications, including Raman spectroscopy and fluorescent imaging, and multiparticle manipulation.

Broadband metasurface-based devices are essential and indispensable in modern wireless communication systems. This paper presents an ultra−wideband and wide incident angle reflective cross−polarization converter metasurface. The unit cell of the proposed structure is a 45° rotated anisotropic meta−sheet developed by cutting the rhombus−shaped patch from the central part of the square patch. The unit cell’s top structure and ground blocking sheet are made of copper, whereas a dielectric substrate (FR−4) is used as an intermediate spacer between them. The unit cell thickness is minimal compared to the operating wavelength (1/14λ∘, where λ∘ is the wavelength of the starting frequency of 13 GHz of the operating band). The proposed structure efficiently converts linearly polarized waves into their orthogonal component, with a polarization conversion ratio of (PCR > 90%) over a broad frequency spectrum of 13 GHz to 26 GHz. The physical origin of polarization conversion is also depicted using surface current distribution plots. An ultra−wideband and highly efficient polarization conversion (above 90%) is achieved with the help of strong electromagnetic resonance coupling between the upper and lower layer of the metasurface. This kind of ultra−wideband polarization conversion metasurface can be employed in satellite communication, radar cross−section reduction, and navigation systems.

This paper presents deep-learning-based image analysis for the detection and classification of road damage, tested for sample images from Ireland. Experimental results showed suitable performance for two of the most prevalent classes of road damage.

peer-reviewed In this work, the digital matched filtering (DMF), a signal processing technique, has been proposed to identify the multiple peak wavelengths, more accurately from reflection spectra of etched few-mode fibre Bragg grating (FM-FBG) sensor. The etched FM-FBG has been fabricated and its intrinsic property of having different sensitivities for different reflection peaks in spectrum has been used for sensing the multiple parameters, such as temperature and refractive index of the ambient environment. The experimental characterization of the fabricated etched FM-FBG sensor has been carried out by using six samples of standard sodium chloride (NaCl(aq)) solutions with refractive indices (RIs) ranging from 1.3159 to 1.3375 at 24 °C temperature. The reflection spectra have been acquired for each sample by varying the temperature from 24 °C to 80 °C. The temperature and RI sensitivities have been investigated from the acquired spectra by using digital matched filter (DMF). The obtained sensor results have been compared with conventional peak detection (CPD) method results for the same spectra. It has been observed that the results obtained by DMF technique are closer to the reference sensor values and has shown more accuracy than the results obtained by CPD technique. It has been shown that the DMF has better performance in terms of the accuracy of measured results than that of CPD. In addition, to eliminate the effect of cross sensitivity issue of the sensor, the 3×3 order characteristic matrix has been used. Hence, the etched FM-FBG can be used as multi-parameter measurements with better performance using DMF technique.

In this paper, the surface roughness characteristic of D-shaped optical fibre sensors with its effects on the sensitivity has been studied. The ULTRAPOL end and edge polishing system was used with some modifications to fabricate the D-shaped sensors with planar sensing zone from the single-mode optical fibres. The mean surface roughness of 343, 96, 25 and 9 nm was estimated at the sensing zone of the D-shaped sensors which were sequentially polished with 30, 9, 3 and 0.5 µm grit size polishing films, respectively. From the experimental results, it has been observed that surface roughness of the sensing zone does not exhibit the significant effects on the output signal strength, whereas the sensitivity of the D-shaped sensors nonlinearly related with the surface roughness of the sensing zone. The designed D-shaped optical fibre sensors have potential applications in biomedical and chemical industries.

The present review provides an overview of the current status and future perspectives of one of the smart manufacturing techniques of Industry 4.0, laser transmission welding (LTW) of semi-crystalline (SC) polymers and their composites. It is one of the most versatile techniques used to join polymeric components with varying thickness and configuration using a laser source. This article focuses on various parameters and phenomena such as inter-diffusion and microstructural changes that occur due to the laser interaction with SC polymers (specifically polypropylene). The effect of carbon black (size, shape, structure, thermal conductivity, dispersion, distribution, etc.) in the laser absorptive part and nucleating agent in the laser transmissive part and its processing conditions impacting the weld strength is discussed in detail. Among the laser parameters, laser power, scanning speed and clamping pressure are considered to be the most critical. This review also highlights innovative ideas such as incorporating metal as an absorber in the laser absorptive part, hybrid carbon black, dual clamping device, and an increasing number of scans and patterns. Finally, there is presented an overview of the essential characterisation techniques that help to determine the weld quality. This review demonstrates that LTW has excellent potential in polymer joining applications and the challenges including the cost-effectiveness, innovative ideas to provide state-of-the-art design and fabrication of complex products in a wide range of applications. This work will be of keen interest to other researchers and practitioners who are involved in the welding of polymers.

A specially designed metallic E-shaped fractal-based perfect metamaterial absorber (PMA) with fairly wideband absorptivity in the K- and Ka-bands of the microwave regime was investigated. The PMA top surface is comprised of square-shaped split-ring resonators (SRRs) surrounded with the stated fractal design. The absorptivity of PMA was analyzed in the range of 20 - 30 GHz for the normal and oblique incidence of waves. Both the transverse electric (TE) and transverse magnetic (TM) modes were taken up to observe the robustness of the proposed design. It was observed that the fractal resonators exhibit capacitive effect at low frequencies, whereas the SRRs manifest capacitive effect at higher frequencies. The simulation and measured results were found to be in fairly good agreement. It is expected that the proposed design of PMA would be useful for 5G communication applications.

Metamaterial-based nano-scale absorbers have been becoming very popular in the modern era due to efficiently absorbing solar radiation to revamp the performance characteristics of thermal emitters and solar thermophotovoltaics (STPV) systems. Here, we explore and implement an ultra-broadband nanostructured metamaterial absorber (NMMA), which comprises a stack of alternating nano-squares of TiN and TiO2 mounted over the dielectric substrate backed by a metallic sheet. The numerical simulations and electromagnetic (EM) characteristics of the proposed NMMA have been investigated by employing the finite difference time domain (FDTD) EM tool. The numerical results indicate that the average absorption of the NMMA reaches 96% in the wavelength range from 200-3000 nm (from ultraviolet to mid-infrared), and the minimal absorption is also above 90% in a continuous large operating spectrum ranging from 200-2800 nm. Surprisingly, the absorption features of the designed nano-absorber remain stable under the influence of oblique incident-angles for both the polarization states (TE & TM). Furthermore, the proposed nano-absorber manifests polarization-insensitive behavior due to the presence of four-fold symmetry of the proposed structure. Large operational bandwidth, miniaturized structure, and the use of thermally stable refractory metal TiN make this NMMA an appealing candidate for the applications of thermal emission, solar thermophotovoltaics, and other opto-electronic devices. In addition, the design of this absorber is also scalable to other operating spectrums through carefully selecting the materials and optimizing the geometry of the proposed structure.

Hardness is a useful measure of a material’s resistance to permanent indentation; but for viscoelastic polymers, hardness data are highly dependent on the test type and the parameter set chosen. Vickers microhardness testing is used to leave small indents (

Traditionally, symmetric accelerating beam (SAB) generation requires bulky optical components, which hinder the miniaturization of optical systems. Recently, metasurfaces, which are composed of sub-wavelength features, have provided a captivating boulevard for the realization of ultra-thin and flat optical devices. Therefore, for the first time, we design and simulate all-dielectric metasurfaces based on an optical caustic approach to generate highly efficient SABs by tailoring the phase of an incident wave. The designed metasurface utilizes spatial distribution of optimized Nb

peer-reviewed The plasmon-induced transparency (PIT) in planar metasurface comprising of resonators having one S-shaped structure and a rectangular strip (both made of silver) was investigated. It was found that the S-shaped component of metasurface induces a single bright mode, whereas the rectangular strip manifests two bright modes with strong coupling of incident electromagnetic waves. When both the metasurface components were placed in the proximity, the PIT-like phenomenon was observed. The effects of rotational angle of the metasurface as well as the angle of incidence on the transmission spectra (of the metasurface) were also investigated. Both the transverse electric (TE) and transverse magnetic (TM) waves were used to explore the PIT effect. It was noticed that the PIT window could be easily tuned by altering the horizontal distance between the resonator components (i.e., the S-shaped structure and rectangular strip). It is expected that the proposed metasurface structure would be prudent in switching, ultrafast sensing and optical applications.

peer-reviewed A novel Fabry-Perot sensor, comprised a glass sphere bonded to a capillary and singlemode fiber, is proposed for refractive index sensing. It is characterized in air, water, ethanol, isopropanol, and glycerol. © 2020 The Author(s)

Achieving the broadband response of metamaterial absorbers has been quite challenging due to the inherent bandwidth limitations. Herein, the investigation was made of a unique kind of visible light metamaterial absorber comprising elliptical rings-shaped fractal metasurface using tungsten metal. It was found that the proposed absorber exhibits average absorption of over 90% in the visible wavelength span of 400–750 nm. The features of perfect absorption could be observed because of the localized surface plasmon resonance that causes impedance matching. Moreover, in the context of optoelectronic applications, the absorber yields absorbance up to ~ 70% even with the incidence obliquity in the range of 0°–60° for transverse electric polarization. The theory of multiple reflections was employed to further verify the performance of the absorber. The obtained theoretical results were found to be in close agreement with the simulation results. In order to optimize the results, the performance was analyzed in terms of the figure of merit and operating bandwidth. Significant amount of absorption in the entire visible span, wide-angle stability, and utilization of low-cost metal make the proposed absorber suitable in varieties of photonics applications, in particular photovoltaics, thermal emitters and sensors.

In recent years, metasurfaces have provided a tempting path to replace conventional optical components where an abrupt phase change is imposed on an incident wave using a periodic array of unit cells. Till date, highly efficient dielectric metasurfaces have been demonstrated in infrared and visible domains. However, due to the lower bandgap of typical dielectric materials, such metasurfaces present strong absorption in the ultraviolet (UV) domain, and thus, hamper their realization at shorter wavelengths. In this paper, we utilize a large bandgap dielectric material, niobium pentoxide (Nb2O5), to construct an ultra-thin and compact transmission-type metasurface that manipulates the phase of an incident wave using an array of Nb2O5 nano-cylinder. By the virtue of numerical optimization, complete 2π phase coverage along with the high transmission efficiency (around 88.5%) is achieved at 355nm. Such efficient control over the phase of the incident wave enabled us to realize the polarisation insensitive self-accelerating parabolic, reciprocal, and logarithmic Airy beams (ABs) generating metasurfaces with the efficiency of 70%, 72% and 77%, respectively. In addition to this, we also demonstrate auto focusing Airy optical vortex (AFAOV) generators where the metasurfaces are designed to combine the phase profiles of an abruptly focusing Airy (AFA) beam and that of spiral phase plate (SPP). The AFAOV is generated with efficiency of 70% (for l = 3) and 72% (for l = 5).

We report a U-bend plastic optical fiber (POF) sensor for measuring ultralow concentration of ethanol corresponding to the initial bioethanol production rate by cyanobacteria, i.e., 0.1–0.5 gL $^{\mathrm {\mathbf {-1}}}$ day $^{\mathrm {\mathbf {-1}}}$ . This production rate corresponds to 0.00499–0.0499 %wt of ethanol in total solution in terms of weight percent concentration. Refractive indices for these minute ethanol concentration values are not available in the literature hence mathematical estimation of the refractive indices for the ethanol-water solutions in this concentration range is demonstrated. The sensing principle is based on optical fiber-based evanescent wave absorption. Parameters affecting the response of an evanescent wave absorption sensor are analyzed for the intended concentration range of ethanol. Experimental results using the U-bend evanescent wave POF sensor are also presented for ethanol-water solutions having refractive indices corresponding to the bioethanol production rate. The excellent repeatability of the measurement is established and these real-time measurements show that sensor has a sensitivity of 817.76 O.D/RIU (O.D refers to optical density, unit of absorbance) with a 99.76% linearity. The limit of detection of the sensor is $9.2\times 10^{\mathrm {\mathbf {-7}}}$ RIU. It is also proved using refractive index calculations of ethanol-water solutions that the sensor exhibits a resolution of $10^{\mathrm {\mathbf {-7}}}$ RIU. The sensor of this investigation, therefore, represents a potential solution for online and real-time monitoring of the production of biofuels even at the very low-level initial concentration of product.

Nano-structure based metamaterial absorbers have been getting enormous interest owing to their widespread applications in solar cells, thermal emitters and integrated photonic devices. This paper presents a novel and ultrathin broadband metamaterial absorber comprised of a hexagonal nano-ring shaped fractal structure. The designed fractal metamaterial absorber (FMA) is composed of a three-layer device having a metal-insulator-metal (MIM) configuration. Based on the numerical simulations, the proposed FMA manifests more than 97% absorptivity for the operating wavelength from 820 to 2520 nm. However, it shows above 80% absorption value for the entire operating wavelength from 200 to 4000 nm. To predict the angular stability of this broadband absorption device, the absorptivity was investigated under different oblique incident angles of the exciting wave by considering both transverse electric (TE)- and transverse magnetic (TM)-polarization. Further, multiple reflection theory was employed to calculate the absorption value of FMA, and it shows appreciable agreement with the simulation results. It is also anticipated that this kind of FMA has not been investigated yet with these ultrabroadband absorption characteristics. Large operating bandwidth, angular robustness, ultra-compact thickness and inclusion of low-cost and temperature-endurable nickel metal (Ni) make this nanostructure-based absorber an attractive candidate for solar photovoltaics, thermal emission, and infrared spectroscopic applications.

Terahertz (THz) metamaterial absorbers have realized a prodigious reputation due to the limitation of natural absorbing materials in this range. Getting wideband absorption characteristics is challenging and arduous, especially in the THz band. Self-similar repeated fractal elements offer a promising solution to attain broadband absorption response due to their inherent multiple resonance characteristics. Therefore, by captivating the advantage of fractal geometry, we proposed a dual and wideband meta-absorber operating in the THz regime. The metamaterial absorber design comprises the assembly of self-similar square-shaped blocks arranged in a specific pattern to construct the fractal geometry. The proposed THz absorber demonstrates 90% absorption under normal incident waves for two operating bands from 9.5–10.55 THz and 12.3–13.35 THz. The suggested metamaterial absorber also shows good and stable absorption responses under different oblique incidence angles for transverse electric (TE) and transverse magnetic (TM) wave polarization. Moreover, this absorber manifests over 85% absorptivity in its entire operating range (9–14 THz) under the incidence angle of 60° and 70° for TM mode. Furthermore, it gives a polarization-insensitive behavior under the effect of different polarization angles. This kind of wideband absorber catches fascinating applications in THz detection, imaging, cloaking, and optoelectronic devices.

This paper reports a polarization controllable and angle-insensitive perfect metamaterial absorber (PMA). The proposed PMA consists of periodically arranged asymmetric omega-shaped resonators made of metallic copper. The absorptivity was analyzed considering the microwave C-band from 4 GHz to 8 GHz. The proposed PMA shows an absorption peak with almost 100% absorptivity at 6.2 GHz. Also, wideband negative index of refraction is observed. Further, the absorber is inspected for the different rotation angles of the top metasurface (omega-shaped ring) along the optical axis, and obliquity of incidence angle for both TE and TM polarized waves. Moreover, surface electric field and surface current distribution were analyzed to understand the absorption mechanism. It was noticed that at resonance (considering 6.2 GHz) electric field maximally remains concentrated on the omega-shaped rings. Furthermore, the simulation and measured results show a good agreement. It is inferred that the proposed PMA would be useful candidate for the sensing and filtering applications in the C-band of the microwave regime.

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A millimeter wave microstrip patch antenna and its array for 5G applications is proposed. The 5G Microstrip patch is designed on rogers RT Duroid 5880 substrate with standard thickness 0.787 mm having relative dielectric constant (∊ r ) = 2.2 and tan δ = 0.0013. The antenna resonates at 24.85 GHz with a return loss -19.5 dB and a bandwidth 1.318 GHz. An array of 1x4 element of the proposed antenna is designed using tapered line feeding. The antenna array resonants at four different frequencies i.e. 23.2 GHz, 27.09 GHz, 31 GHz and 42.5 GHz. Appreciable improvement in gain is observed with the array of antennas. The antenna and its array can be used for 5G mobile communication because of its compactness.