T Dias

Fibre-meshed transducers based real time wearable physiological information monitoring system

Unobtrusive sensors are an important element in wearable systems. One approach in constructing unobtrusive transducers is to use smart materials and then integrate them into smart unobtrusive fabric structures. These types of transducers are called fabric transducers (Fibre-Meshed Transducers or FMTs). Fabrication is carried out via textiles manufacturing processes. In this paper we have discussed three types of FMTs and their applications. Also the discussion is further extended towards real time physiological monitoring system. We have constructed resistive, inductive and capacitive transducers with electronic flatbed knitting technology. The resistive FMTs that were developed inherited with limitations. The inductive FMTs are used for motion and gesture capturing of the kinematical joints of the human body, and capacitive FMTs are used as bio-potential electrodes, which were used to measure ECG. Also we have used the capacitive FMTs as switches. Further we have developed a PDA based wearable physiological monitoring system by using these novel FMTs.

Resistive fibre-meshed transducers

The paper demonstrates the preliminary researchcarried out on fibre meshed transducers for wearablecomputing applications, their constructions using electro-conductive fibres via the route of modern electronicflatbed knitting technology. The paper reports theconstruction of resistive strain and displacementtransducers using electroconductive polymeric fibres(resistivity of 104?cm-1) and metallic fibres (resistivity of10?cm-1) and the modelling of electrical equivalentcircuits of the fibre meshed transducers. The models arediscussed in order to demonstrate the variation ofelectrical parameters under static and dynamic planarloads. Two methods of transducer construction are alsodiscussed; in the first method the electroconductive fibresare stretched out in the base fibre meshed structure, andin the second method the electroconductive fibres areintermeshed as an integral section of the base fibremeshed structure.

The influence of moisture content on the thermal conductivity of a knitted structure

A theoretical model has been created to predict the thermal conductivity of knitted structures in terms of porosity, thickness and moisture content. The validity of the model was examined by the results of experiments conducted using different knitted fabrics, in which the porosity, thickness, fibre and water content are different. The thermal conductivity of a dry plain knitted fabric decreases with the increase of porosity; however, with increased water content, the increase of porosity contributes to an increase in thermal conductivity.

Knittability of High-modulus Yarns

The knitting of filamentary high-modulus yarns on V-bed and circular machines is reported in this paper. A theoretical study of the breaking of glass filaments during knitting is presented. The influence of yarn and knitting parameters on the knittability of high-modulus yarns is also discussed.

Sound absorbtion in knitted structures for interior noise reduction in automobiles

Reduction of interior noise in modern automobiles is an important issue in the automobile industry. Textiles are one solution, as they can provide passive sound absorption in upholstery, headliners and other interior parts. Nonwovens have also been used, but they have a lesser aesthetic appearance and drapability compared with woven and knitted structures, which can provide a 3D seamless fabric and have a pleasing appearance. In this paper we test the sound absorption of plain knitted fabrics and compare this with a theoretical model.

Analysis of sound absorption of tuck spacer fabrics to reduce automotive noise

Textiles are widely used in the automotive industry to provide both comfort to the passengers and an aesthetic appearance to the automotive interior. They can also be used to reduce automotive interior noise, which can make automotive travel safer and more comfortable. Knitted fabrics are used widely in automotive upholstery; however, the sound absorbency of a single layer of a knitted fabric is inadequate for the reduction of automotive interior noise. This paper investigates the sound absorbency of a novel knitted spacer fabric, which can be used in automotive upholstery and has the potential for greater sound absorbency than a conventional plain knitted fabric and its derivatives. The spacer fabric is modelled as a porous sound absorber and its sound absorbency is studied with regard to its structural parameters.

Analysis of thick spacer fabrics to reduce automobile interior noise

Textile structures have the potential to reduce interior noise in an automobile; here the sound absorption of a novel knitted spacer fabric is discussed. The spacer fabric was analysed as a micro perforated panel absorber, a simulation being carried out on the effect of the structural properties of the fabric on its sound absorption capability. This mathematical analysis was then validated by suitably knitted spacer fabric samples. The results show a significant improvement in sound absorption compared to planar knitted structures.

Capacitive fiber-meshed transducers for touch and proximity-sensing applications

Capacitive sensing is used in manufacturing E-textiles for touch and proximity-sensing applications. The common approach is to construct electrodes on top of a nonconductive fabric structures. Woven and knitted fabric structures are used for the construction; metallic wire and conductive coated fibers are primarily used. Due to the performance degradation and poor comfort of these constructions, we have constructed electrodes with inherently conductive polymers and multifilament metallic fibers by integrating them into fiber-meshed structures such that the electrodes are a part of the nonconductive base structure. We have used capacitive and resistive measurement techniques for the detection. Out of many mechanical methods of fiber-integrating processors, we have used flat bed-knitting technology and Jacquard weaving technology. In this paper, we have discussed the construction, sensing, and applications of capacitive fiber-meshed transducers and their applications.

Automatic identification of gait events using an instrumented sock

BackgroundTextile-based transducers are an emerging technology in which piezo-resistive properties of materials are used to measure an applied strain. By incorporating these sensors into a sock, this technology offers the potential to detect critical events during the stance phase of the gait cycle. This could prove useful in several applications, such as functional electrical stimulation (FES) systems to assist gait.MethodsWe investigated the output of a knitted resistive strain sensor during walking and sought to determine the degree of similarity between the sensor output and the ankle angle in the sagittal plane. In addition, we investigated whether it would be possible to predict three key gait events, heel strike, heel lift and toe off, with a relatively straight-forward algorithm. This worked by predicting gait events to occur at fixed time offsets from specific peaks in the sensor signal.ResultsOur results showed that, for all subjects, the sensor output exhibited the same general characteristics as the ankle joint angle. However, there were large between-subjects differences in the degree of similarity between the two curves. Despite this variability, it was possible to accurately predict gait events using a simple algorithm. This algorithm displayed high levels of trial-to-trial repeatability.ConclusionsThis study demonstrates the potential of using textile-based transducers in future devices that provide active gait assistance.

Development and analysis of novel electroluminescent yarns and fabrics for localized automotive interior illumination

Textiles used in automotive interiors can be used to provide localized illumination if made to illuminate. In this study a novel electroluminescent (EL) yarn has been developed that can be integrated with knitted and woven fabrics. An EL yarn construction and an appropriate EL coating have been studied; moreover, a novel automated single yarn coating system has also been developed. An analytical model of the luminance of this yarn was also created based on alternating current thin-film EL technology. An automated EL yarn driver system, which electrically drives the yarn to provide illumination, and an illuminance measurement system to detect its illumination have been explained. The luminescence of the EL yarn has been analyzed based on the luminance derived by the analytical model and the illuminance detected by the measurement system. Finally, knitted fabrics integrated with this yarn are described with possible applications in automotive or aerospace interiors.