Polypyrrole based electro-conductive textiles for heat generation

This work deals with the preparation and characterization of electrically conductive textiles for heat generation. Needlepunched nonwoven, spunlace nonwoven, and woven fabrics, all made of 100% polyester fibers, were made electrically conductive by in situ chemical polymerization of pyrrole with p-toluene sulfonic acid dopant. Alkali hydrolysis of polyester fabrics was done before in situ polymerization for better fixation of polypyrrole on polyester. The average surface resistivities were found to be 1013.08, 1099.72, and 1434.12?Ω/□, respectively, for needlepunched, spunlace, and woven fabrics. The electro-conductive fabrics displayed exponential rise of surface temperature on application of voltage and the rise of temperature was found to be related to the time duration of applied voltage. The electro-conductive fabrics exhibited linear voltage–current relationship at low voltage range. The surface resistivity of the electro-conductive fabrics was increased substantially on prolong exposure to atmosphere.     

Influence of graphene oxide concentration and dipping cycles on electrical conductivity of coated cotton textiles

The electrical conductivity of cotton fabrics is enhanced by coating with graphene in aqueous phase by a suitable process. Two different types of fabrics viz. woven and knitted structures of same GSM are used as substrate. The fabrics are dipped in dispersed graphene oxide (GO) solution and then GO-enriched fabric samples are subjected to a reduction process for in-situ conversion of the added GO to electro-conductive graphene. The concentration of GO solution and number of dipping cycles influence the graphene add-on and electrical resistivity of the fabrics. The change in surface resistivity, thickness, air permeability, porosity and water vapour permeability of the fabrics after the treatment has been evaluated. Comparisons have been made between the woven and knitted fabrics for all these properties to understand the effect of fabric structure.     

基于力敏发热的智能纺织品设计

采用石墨烯、碳纳米管、聚吡咯等导电导热材料,在两层织物的上层以方格形式印刷石墨烯涂料,下层织入导电纱线。运用多学科知识,采用上下层织物接触导通电路的方式,以压力为条件在接触区域产生热能的新颖电热原理,设计了具有受压局部发热且温度可调功能的新型智能纺织品,该纺织品具有可折叠变形、节能简约、安全度高、实用便捷等特点,可以用于食品的恒温保温、汽车飞机座椅加热、康复医疗等各种领域。文章从纱线材料、织物组织结构、电路分析等方面对智能纺织品进行设计研发。     

The influence of distribution and deposit of conductive coating on shielding effectiveness of textiles

This study presents the investigation of electrically conductive fabrics with low resistivity, coated with formulation containing the conjugated polymer system – poly(3,4-ethylenedioxythiophene)-polystyrene sulphonate (PEDOT-PSS). The samples of fabrics were coated with PEDOT-PSS, using a screen printing method, by different patterns or coating their surface fully with different coating deposit. Methods for measurement of electrostatic properties, reflection and transmission as well as the assessment of electromagnetic radiation (EMR) shielding effectiveness were used for the characterization of electrical properties of developed samples. EMR shielding properties were investigated within 2–12 GHz frequency bands. The highest attenuation of the electromagnetic energy among tested fabrics was obtained on the fabrics fully coated with paste and it depended on deposit considerably. The influence of distribution and deposit of conductive coating on shielding effectiveness of textiles were determined. Correlation between shielding effectiveness and electrostatic properties of developed coated fabrics was also discussed. Electrical properties of samples coated with formulation containing PEDOT-PSS were compared with these of fabrics with metalized yarns, developed by us earlier. The results of EMR shielding measurements showed that fabrics coated with the paste containing conductive polymer system compared to fabrics with in-weaved conductive metalized yarns have certain advantages as EMR shields.     

Impact of storage environment on the efficacy of hermetic storage bags

Small hermetic bags (50 and 100 kg capacities) used by smallholder farmers in several African countries have proven to be a low-cost solution for preventing storage losses due to insects. The complexity of postharvest practices and the need for ideal drying conditions, especially in the Sub-Sahara, has led to questions about the efficacy of the hermetic bags for controlling spoilage by fungi and the potential for mycotoxin accumulation. This study compared the effects of environmental temperature and relative humidity at two locations (Indiana and Arkansas) on dry maize (14% moisture content) in woven polypropylene bags and Purdue Improved Crop Storage (PICS) hermetic bags. Temperature and relative humidity data loggers placed in the middle of each bag provided profiles of environmental influences on stored grain at the two locations. The results indicated that the PICS bags prevented moisture penetration over the three-month storage period. In contrast, maize in the woven bags increased in moisture content. For both bag types, no evidence was obtained indicating the spread of Aspergillus flavus from colonized maize to adjacent non-colonized maize. However, other storage fungi did increase during storage. The number of infected kernels did not increase in the PICS bags, but the numbers in the woven bags increased significantly. The warmer environment in Arkansas resulted in significantly higher insect populations in the woven bags than in Indiana. Insects in the PICS bags remained low at both locations. This study demonstrates that the PICS hermetic bags are effective at blocking the effects of external humidity fluctuations as well as the spread of fungi to non-infected kernels.     

电加热高空清洁作业服研制与性能评价

高空清洁人员在高空环境下常面临严重的低温气候威胁,为提高高空清洁作业服的保暖性能,设计开发了一款电加热高空清洁作业服。在模拟的高空作业环境(温度为(5 ± 0.5) ℃,相对湿度为(60 ± 5)%)下,通过人体穿着电加热高空清洁作业服的实验对皮肤温度和运动舒适性进行测试和评价。结果表明:穿着电加热高空清洁作业服可更好地维持人体平均皮肤温度,且时间越长,保暖效果越显著;将电加热片放置在后背可有效提高躯干皮肤温度,同时不会影响人体背部局部的主观热舒适性;结构上采用局部插片和暗褶设计可有效提高高空清洁作业服的活动自由度。     

Coating of conductive yarns for electro-textile applications

Conductive yarns are used for integration of sensors and other electronic devices with textile fabrics through weaving, knitting, braiding or embroidery processes. In the lifetime of the textile also several washing cycles might occur. These processes involve rubbing which may lead to displacement of conductive fibres, causing short circuiting between the neighbouring conductive fibres. Also the textile products made with conductive fibres may have to work in the presence of water, where the exposed conductive fibres can get short circuited. In this work, an attempt has been made to protect silver-coated polyamide yarns with polypropylene (PP). This is done through wrapping the PP staple fibres around the silver-coated polyamide yarns through friction spinning and melting the PP sheath fibres in an oven. The influence of twist in the conductive yarns, amount of PP coating and the oven temperature during coating process on the tenacity, electrical insulation in the presence of water and flexibility properties of the coated yarns are studied. The PP coated yarns with plied conductive yarn in the core provide better flexibility but need higher amount of coating to provide complete electrical insulation in the presence of water as compared to those yarns with single conductive yarn in the core.     

Determinants of electrical resistance change of in situ PPy-polymerized stretch plain woven fabric under uniaxial tensile strain

Although the conductive stretchable woven fabric has been widely used as the sensitive material of strain sensors monitoring human motion, it is lack of a deep understanding of the determinants of its electrical resistance change under uniaxial tensile strain. This study chose two kinds of typical stretchable plain woven fabric, i.e. cotton/spandex core-spun yarn fabric and polyester/spandex filament yarn fabric, and they were coated by in situ polymerization of polypyrrole. Their electromechanical responses under certain uniaxial tensile loadings were measured and compared. Meanwhile, by a multi-architecture analysis, i.e. the intrinsic resistance of yarns, the contact resistance of interlacing yarns and the contact resistance of adjacent yarns in parallel, several hypotheses were proposed and tested to determine the determinants of electrical resistance change under tensile strains. The results showed that the resistance change in woven fabric with in situ polymerization of polypyrrole mainly depends on the contact resistance of the adjacent conductive yarns in tensile direction, and the electromechanical responses of the cotton/spandex core spun yarn are significantly different from those of the polyester/spandex filament yarn. It was concluded that the conductive yarn density and fabric structure are critical parameters of woven fabric as resistive strain sensor.     

The electromagnetic shielding properties of some conductive knitted fabrics produced on single or double needle bed of a flat knitting machine

In recent years, the use of electrical and electronic devices has grown rapidly. These devices cause electromagnetic interferences, which could threaten human life. In order to solve this problem, intensive research to develop textile surfaces having electromagnetic shielding properties continues. In this paper, we study textile surfaces knitted with conductive copper and stainless steel wires wrapped with acrylic yarns and also core yarns produced by using conductive yarns to test the electromagnetic shielding properties of the fabrics. It was concluded that the knitted structure of the fabrics affected the electromagnetic shielding effectiveness (EMSE). Besides, the fabrics knitted on a double needle bed of the knitting machine with higher amounts of conductive yarns and unit weights could not provide the targeted improvement in the EMSE values with respect to the fabrics produced on a single needle bed of the knitting machine.     

Modeling and optimizing the frictional behavior of woven fabrics in climatic conditions using response surface methodology

Frictional characteristics of woven fabrics can determine smoothness and softness values of textiles. In this paper, we have studied the influence of factors such as temperature, relative humidity, fabric structure, type of fiber material, and direction of motion on roughness properties of fabric surface using response surface method (RSM). For this purpose, woven fabrics with plain, rib2/2, twill2/2, twill1/3, twill3/1, twill1/7, and twill7/1 were produced with polyester warp yarn and two different weft yarns (cotton and polyester). Then, a statistical model (RSM) was used for the experimental plan (with these variables) to determine the runs of experiment (or selected points). Next, the frictional forces measurement was carried out on the fabrics in those directions. The experimental results showed that fabric-to-fabric friction (static frictional resistance, kinetic frictional resistance, and smoothness of woven fabrics) is highly sensitive to factors like relative humidity, fabric structure, type of fiber material, and direction of motion while temperature factor (in the range 0–50°C) has no sensitive effect on frictional parameters.     

An investigation about comfort and protection performances of disposable and reusable surgical gowns by objective and subjective measurements

This study was conducted to investigate comfort and microbial protection performances of two reusable and two disposable surgical gowns by subjective wear trials conducted on eight healthy Dentistry faculty students under environmental conditions suitable for a surgical operation. Protection performances of the gowns were tested by a modified bacterial resistance test. Physiological and psychological data were obtained during wear trials. All objective and subjective results were evaluated in the light of standard physical, mechanical, permeability, and resistance (thermal and water vapor) characteristics of the fabrics. According to the results, thermal comfort performance of the woven gown produced from microfiber polyester was the best according to subjective wear trial and microbial resistance test results. Disposable nonwoven gowns had lower comfort performances despite their higher permeability and lower resistance values. Moreover, chest skin temperature, arm microclimate temperature, and arm relative humidity are the physiological parameters significantly correlated with subjective comfort evaluation results.     

Development and characterization of conductive ring spun hybrid yarns

Development of conductive yarns for smart textile applications is the most demanding area of research these days. This study was aimed to investigate the effect of yarn constructional parameters, and relative humidity on electromechanical properties of conductive ring spun hybrid yarns. Stainless steel (SS) fibre was blended with polyester and viscose fibre separately on 12% and 24% weight basis to produce hybrid conductive yarns at three different levels of twist factor. The electromechanical properties of yarns were evaluated in response to change in blend type, blend ratio, twist factor, and relative humidity. The content of SS fibre is found to be more effective followed by the twist factor and blend type to govern the linear electrical resistance (LER) of conductive yarns. In addition, on increasing relative humidity, the LER of viscose stainless steel (VS) hybrid yarns are found to drop significantly than that of polyester stainless steel (PS) hybrid yarns.     

远程监控服装在人员监控上的应用

探讨了远程监控服装（TG）采用的监控人员身体状况的系统。TG由电导、光导纤维织成的网和普通的机织或刺绣织物整合而成,普通织物所选用的纤维和纱线能满足服用舒适性和耐用性。最初的TG传感服是用于改进野战医院伤员的鉴别归类（根据紧迫性和救活的可能性等可在战场上决定优先治疗的人员的方法）。     

Ohmic Heating of an Electrically Conductive Food Package

Ohmic heating through an electrically conductive food package is a new approach to heat the food and its package as a whole after packing to avoid post‐process contamination and to serve consumer needs for convenience. This process has been successfully completed using polymer film integrated with an electrically conductive film to form a conductive package. Orange juice packed in the conductive package surrounded with a conductive medium was pasteurized in an ohmic heater. A mathematical model was developed to simulate the temperature distribution within the package and its surroundings. A 3‐D thermal‐electric model showed heating uniformity inside the food package while the hot zone appeared in the orange juice adjacent to the conductive film. The accuracy of the model was determined by comparing the experimental results with the simulated temperature and current drawn; the model showed good agreement between the actual and simulated results. An inoculated pack study using Escherichia coli O157:H7 indicated negative growth of viable microorganisms at the target and over target lethal process temperatures, whereas the microorganism was present in the under target temperature treatment. Consequently, our developed ohmic heating system with conductive packaging offers potential for producing safe food.     

Flexible non-metallic electro-conductive textiles

This issue of Textile Progress reviews research carried out on electrically conducting polymers, fibres and fabrics prepared by in situ chemical, electrochemical and vapour-phase polymerisation. It provides information about various inherently conducting polymers prepared from aniline, pyrrole, thiophene and their derivatives that are often used to prepare flexible non-metallic electro-conductive textiles. Several methods for the characterisation of electro-conductive fabrics are included, namely scanning electron microscopy, X-ray diffraction, elemental disruptive X-ray analysis and Fourier transmission infrared spectroscopy. The role of the polymerisation process in determining the electrical properties of electro-conductive textiles is examined. The review highlights applications of flexible non-metallic conductive textiles in electro-magnetic shielding materials, heating pads, sensors and actuators.     

Development of a low cost optimized handheld embedded odor sensing system (HE-Nose) to assess ripeness of oranges

Presented work addresses the development and application of artificial olfactory (e-nose) as an efficient nondestructive handheld system to extract quality attributes of variety of orange cultivars at various cultivated lands. An ARM-9 (S3C2440 controller) based advance embedded electronic nose system has been developed for on-site odor acquisition, processing and ripeness level prediction for various orange cultivars. Developed handheld electronic nose system is light weight, low power, and easy operable to every consumer. Various statistical multivariate data analysis techniques (PCA, LDA, QDA, and KNN) implementation on electronic nose measurements helped estimating optimal harvest dates for various orange cultivars. Developed handy system has been optimized in the sense of selectivity, sensitivity of gas sensors using the implementation of temperature control for heating element of the gas sensors. Various temperature, humidity models also have been developed to improve the performance of developed system in different environmental conditions. Data acquisition process has been performed using developed system for 100 orange samples have two different cultivars (mandarin and sweet orange). Extracted parameters have been subjected towards supervised Levenberg–Marquardt back-propagation algorithm to training and testing of developed handheld electronic nose system to predict quality parameters of oranges. A good correlation has been found between developed handheld electronic nose system signals and quality attributes indicators and it shows that system can successfully detect and predict various quality parameters of orange samples. Results of developed handheld electronic nose system have been validated with commercial standard electronic nose Alpha Fox 3000 system and it has been observed that efficiency varies around 94 ± 0.3 %.     

喷墨打印导电墨水及其智能电子纺织品研究进展

为进一步推动印刷电子技术在纺织领域的应用并拓宽智能电子纺织品的应用领域,简要介绍了喷墨打印技术的电路印制过程和导电墨水组成;从当前喷墨打印技术中导电墨水存在的主要问题出发,详细综述了国内外导电墨水中金属系、碳系、高分子系导电组分的研究进展。以纺织基电子器件的柔性应用为出发点,主要介绍了喷墨打印技术在柔性导电器件、智能传感和能源采集与转换等应用领域的研究进展,为基于喷墨打印技术的智能电子纺织品的发展提供了理论与实践参考。最后,对印刷电子技术的技术要素、技术发展和应用前景等方面进行了总结与展望,指出智能打印及柔性应用是其未来的发展方向。     

Numerical investigation of the heat transfer through woven textiles by the jet system theory

The paper presents a numerical study on the heat transfer in through-thickness direction of single woven layers, based on the jet system theory. A mathematical model, involving the Reynolds-Averaged Navier-Stokes partial differential equations is used, and two turbulence models (k ? ? and RSM) are applied to solve the closure problem. Numerical results for the temperature distribution, heat rate, heat flux and thermal resistance of the samples are obtained, analyzed, and validated by experimental data. The presented approach for modeling the heat transfer through woven macrostructures is concluded to be a working numerical tool that has the potential to replace costly design iterations and experiments to produce woven textiles with desired performance.     

Effect of weft density and percentage of stainless steel fiber content of weft yarn on electrical properties of woven fabric strain sensors

Textile-based strain sensors have been used in smart textiles frequently. In this study, effect of percentage of stainless steel fiber of spun yarn (i.e. 28 and 40%) and weft density (i.e. 14, 18, and 22 per cm) of conductive yarn on performance and sensitivity of woven fabrics strain sensor under tensile cyclic loading in 3 mm elongation and also behavior of woven fabric strain sensors under simple tensile loading, was studied. Our finding showed the interaction between weft density and percentage of conductive fiber of spun yarns on performance and sensitivity of strain sensors under cyclic loading. Samples prepared by conductive yarns with 40% stainless steel fiber showed no clear cyclic variation in 18 and 22 weft per cm. This trend for samples woven with conductive yarn with 28% stainless steel fiber was only observed in 22 weft per cm. All samples showed the same trend of resistance variation during simple tensile loading, although the level of resistance variation was different. The slope of resistance variation during tensile cyclic loading confirmed plastic deformation of samples. Finally, by comparing the sensitivity of strain sensors during cyclic loading no obvious advantage was obtained for samples woven with conductive yarn with 40% stainless steel fiber compared with samples woven with conductive yarn with 28% stainless steel fiber.     

Textile electrodes of jacquard woven fabrics for biosignal measurement

In the last few years, textile electrodes have become an interesting topic for physiological monitoring, steadily developing to be applied in innovative wearable sensing systems. The structure of textile electrodes can be fabricated by weaving, knitting, or embroidering conductive yarn and is now commercially available. The upgraded textile electrode is used in biosignal sensing and was designed in the form of a jacquard woven structure to measure the ECG. In the case of knit fabric, which has piezo‐resistive properties, the textile electrodes were developed by using the fabric’s flexible strain gauges in a bio‐monitoring system. However, the piezo‐resistive sensing fabrics have some shortcomings such as low dynamic range, poor repeatability, and performance deterioration after washing or repeated folding. Woven fabric, which is cloth woven in the warp and weft directions, has less strain properties and can be constructed more uniformly than knit fabric. Therefore, due to their more consistent woven structure, jacquard woven fabrics made with conductive yarn can be manufactured evenly on a large scale and consistently maintain their properties. The woven structure of jacquard electrodes consists of a double‐faced weave and is woven with a silver covering yarn in the weft direction. The proposed textile electrodes were composed of two groups made up of warps with either the unremoved 100% warps or the half‐removed 50% warps of jacquard woven electrodes that were convex or flat and were either with or without conductive paste. The ECG measurements for the textile electrodes were repeated three times in resting conditions. The convex jacquard electrodes of the half‐removed 50% warps with the conductive paste resulted in the most significant SNR improvement (33.67 dB). The purpose of this paper was to investigate a method to design jacquard woven electrodes uniformly on a large scale and to apply it feasibly to ECG measurement.