Cédric Cochrane

A Flexible Strain Sensor Based on a Conductive Polymer Composite for in situ Measurement of Parachute Canopy Deformation

A sensor based on a Conductive Polymer Composite (CPC), fully compatible with a textile substrate and its general properties, has been developed in our laboratory, and its electromechanical characterization is presented herein. In particular the effects of strain rate (from 10 to 1,000 mm/min) and of repeated elongation cycles on the sensor behaviour are investigated. The results show that strain rate seems to have little influence on sensor response. When submitted to repeated tensile cycles, the CPC sensor is able to detect accurately fabric deformations over each whole cycle, taking into account the mechanical behaviour of the textile substrate. Complementary information is given concerning the non-effect of aging on the global resistivity of the CPC sensor. Finally, our sensor was tested on a parachute canopy during a real drop test: the canopy fabric deformation during the critical inflation phase was successfully measured, and was found to be less than 9%.

New design of textile light diffusers for photodynamic therapy

A homogeneous and reproducible fluence delivery rate during clinical photodynamic therapy (PDT) plays a determinant role in preventing under- or overtreatment. PDT applied in dermatology has been carried out with a wide variety of light sources delivering a broad range of more or less adapted light doses. Due to the complexities of the human anatomy, these light sources do not in fact deliver a uniform light distribution to the skin. Therefore, the development of flexible light sources would considerably improve the homogeneity of light delivery. The integration of plastic optical fiber (POF) into textile structures could offer an interesting alternative. In this article, a textile light diffuser (TLD) has been developed using POF and Polyester yarns. Predetermined POF macrobending leads to side emission of light when the critical angle is exceeded. Therefore, a specific pattern based on different satin weaves has been developed in order to improve light emission homogeneity and to correct the decrease of side emitted radiation intensity along POF. The prototyped fabrics (approximately 100 cm(2): 5×20 cm) were woven using a hand loom, then both ends of the POF were coupled to a laser diode (5 W, 635 nm). The fluence rate (mW/ cm(2)) and the homogeneity of light delivery by the TLD were evaluated. Temperature evolution, as a function of time, was controlled with an infrared thermographic camera. When using a power source of 5 W, the fluence rate of the TLD was 18±2.5 mw/cm(2). Due to the high efficiency of the TLD, the optical losses were very low. The TLD temperature elevation was 0.6 °C after 10 min of illumination. Our TLD meets the basic requirements for PDT: homogeneous light distribution and flexibility. It also proves that large (500 cm(2)) textile light diffusers adapted to skin, but also to peritoneal or pleural cavity, PDTs can be easily produced by textile manufacturing processes.

Light Emitting Fabric Technologies for Photodynamic Therapy.

Photodynamic therapy (PDT) is considered to be a promising method for treating various types of cancer. A homogeneous and reproducible illumination during clinical PDT plays a determinant role in preventing under- or over-treatment. The development of flexible light sources would considerably improve the homogeneity of light delivery. The integration of optical fiber into flexible structures could offer an interesting alternative. This paper aims to describe different methods proposed to develop Side Emitting Optical Fibers (SEOF), and how these SEOF can be integrated in a flexible structure to improve light illumination of the skin during PDT. Four main techniques can be described: (i) light blanket integrating side-glowing optical fibers, (ii) light emitting panel composed of SEOF obtained by micro-perforations of the cladding, (iii) embroidery-based light emitting fabric, and (iv) woven-based light emitting fabric. Woven-based light emitting fabrics give the best performances: higher fluence rate, best homogeneity of light delivery, good flexibility.

PEDOT:PSS-Based Piezo-Resistive Sensors Applied to Reinforcement Glass Fibres for in Situ Measurement during the Composite Material Weaving Process

The quality of fibrous reinforcements used in composite materials can be monitored during the weaving process. Fibrous sensors previously developed in our laboratory, based on PEDOT:PSS, have been adapted so as to directly measure the mechanical stress on fabrics under static or dynamic conditions. The objective of our research has been to develop new sensor yarns, with the ability to locally detect mechanical stresses all along the warp or weft yarn. This local detection is undertaken inside the weaving loom in real time during the weaving process. Suitable electronic devices have been designed in order to record in situ measurements delivered by this new fibrous sensor yarn.

Evaluation of Solid or Liquid Phase Conducting Polymers Within a Flexible Textile Electrochromic Device

Conducting polymers, in both their solid or liquid states, have been successfully employed within a novel flexible 4-layer electrochromic prototype device. The device consists of the polymer combined with a flexible PET textile spacer, sandwiched between two electrodes - one of which is applied on a flexible textile substrate. The electrochromic materials that have been employed are polyaniline and substituted polythiophene polymers. Two methods of preparation have been used. Aniline was chemically polymerized to the surface of the PET textile substrate, in its solid state, prior to application within the device. Conversely, substituted thiophene monomers, in the solution phase, were suspended within the textile spacer and electrochemically polymerized in situ within the device. The application of an electrical voltage ( ±3 V) effects a reversible color change for both solid and liquid phase systems, providing a flexible communicative textile with applications for protection and safety purposes, or for added fashion. This paper outlines the preparation and characterization of each of the solid and liquid electrochromic display systems and discusses the benefits and drawbacks of each.

Development of a Flexible Strain Sensor Based on PEDOT:PSS for Thin Film Structures

The aim of this study was to develop and optimize a reproducible flexible sensor adapted to thin low-density polyethylene (LDPE) films and/or structures to enable their deformation measurements. As these deformations are suspected to be weak (less than 10%), the developed sensor needs to be particularly sensitive. Moreover, it is of prime importance that sensor integration and usability do not modify the mechanical behavior of its LDPE substrate. The literature review allowed several materials to be investigated and an elastomer/intrinsically conductive polymer PEDOT:PSS (CleviosTM) filled composite was selected to simultaneously combine mechanical properties and electrical conductivity. This composite (made of PEDOT:PSS and silicone Bluesil®) presented satisfying compatibilities with piezoresistive effects, negative temperature performances (in a range from −60 °C to 20 °C), as well as elongation properties (until the elastic limit of the substrate was reached). The method used for creating the sensor is fully described, as are the optimization of the sensor manufacture in terms of used materials, the used amount of materials where the percolation theory aspects must be considered, the adhesion to the substrate, and the manufacturing protocol. Electromechanical characterization was performed to assess the gauge factor (K) of the sensor on its substrate.

Washable and Reliable Textile Electrodes Embedded into Underwear Fabric for Electrocardiography (ECG) Monitoring

A medical quality electrocardiogram (ECG) signal is necessary for permanent monitoring, and an accurate heart examination can be obtained from instrumented underwear only if it is equipped with high-quality, flexible, textile-based electrodes guaranteeing low contact resistance with the skin. The main objective of this article is to develop reliable and washable ECG monitoring underwear able to record and wirelessly send an ECG signal in real time to a smart phone and further to a cloud. The article focuses on textile electrode design and production guaranteeing optimal contact impedance. Therefore, different types of textile fabrics were coated with modified poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) in order to develop and manufacture reliable and washable textile electrodes assembled to female underwear (bras), by sewing using commercially available conductive yarns. Washability tests of connected underwear containing textile electrodes and conductive threads were carried out up to 50 washing cycles. The influence of standardized washing cycles on the quality of ECG signals and the electrical properties of the textile electrodes were investigated and characterized.

Light-Emitting Woven Fabric for Treatment with Photodynamic Therapy and Monitoring of Actinic Keratosis

A successful photodynamic therapy (PDT) requires a specific photosensitizer, oxygen and light of a specific wavelength and power. Today photodynamic therapy (PDT) is administered to patients with light-emitting diode (LED) panels. These panels deliver a non-uniform light distribution on the human body parts, as the complex human anatomy is not a flat surface (head vertex, hand, shoulder, etc.). For an efficient photodynamic therapy (PDT), a light-emitting fabric (LEF) was woven from plastic optical fibers (POF) aiming at the treatment of dermatologic diseases such as actinic keratosis (AK). Plastic optical fibers (POF) (Toray, PGR-FB250) have been woven in textile in order to create macro-bendings, and thus emit out the injected light directly to the skin. The light intensity and light-emitting homogeneity of the LEF were improved thanks to Doehlert Experimental Design. During the treatment with PDT, the photosensitizers were activated in the cancerous cells. These cells may be visualized, as they show a characteristic fluorescence under UV light, which is called fluorescence diagnosis (FD). Therefore, it is proposed to modify the developed LEF for PDT to measure the fluorescence amount. For this aim, a part of POFs was cut out to observe the quantity of light that could be collected while the LEF was connected to a light source. The first prototypes showed the possibility of the illumination with the same LEF without losing the efficiency but also imaging the collected light.

Smart textiles in automotive interiors

In this chapter different smart textile structures suitable for use in car interiors are presented. One of the main interests of smart textile integration in car interiors is also related to the ‘customization’ trend. Designing very low weight car seats with heating fabric and achieving space saving and comfort thanks to a more breathable structure are now possible. However, only few applications can be found today involving smart textile structures comprising sensors, actuators, and computing and storage devices integrated into internal car elements. On the other side, car interiors contain a range of textile surfaces that may host textile-based sensors and actuators adapted to this specific space. They may be classified in function of the measured parameters and effects they are able to generate. This classification is given below: • Sensors: temperature, humidity, strain, UV radiation, acceleration, light intensity, etc.

Woven metamaterials with an electromagnetic phase-advance for selective shielding

This study deals with the development of a large woven metamaterial surface for applications in the submillimeter frequency band. Before weaving, design of the metamaterial textile is investigated to obtain a phase-advance near 500 GHz. Then, a large sample is produced by semi-industrial machine and characterized in terms of dimensional homogeneity and electromagnetic behaviours in the frequency band [325 – 700 GHz]. Dimensional heterogeneity is measured to be less than 2% and shows that weaving process is well controlled. A phase-advance and high-pass filter behaviors are experimentally evidenced by electromagnetic characterizations with potential applications for selective shielding and phase manipulation of the wave.