Smart nanotextiles: materials and their application

Textiles are ubiquitous to us, enveloping our skin and surroundings. Not only do they provide a protective shield or act as a comforting cocoon but they also serve esthetic appeal and cultural importance. Recent technologies have allowed the traditional functionality of textiles to be extended. Advances in materials science have added intelligence to textiles and created ‘smart’ clothes. Smart textiles can sense and react to environmental conditions or stimuli, e.g., from mechanical, thermal, chemical, electrical, or magnetic sources (Lam Po Tang and Stylios 2006). Such textiles find uses in many applications ranging from military and security to personalized healthcare, hygiene, and entertainment. Smart textiles may be termed ‘‘passive’’ or ‘‘active.’’ A passive smart textile monitors the wearer’s physiology or the environment, e.g., a shirt with in-built thermistors to log body temperature over time. If actuators are integrated, the textile becomes an active, smart textile as it may respond to a particular stimulus, e.g., the temperature-aware shirt may automatically roll up the sleeves when body temperature rises. The fundamental components in any smart textile are sensors and actuators. Interconnections, power supply, and a control unit are also needed to complete the system. All these components must be integrated into textiles while still retaining the usual tactile, flexible, and comfortable properties that we expect from a textile. Adding new functionalities to textiles while still maintaining the look and feel of the fabric is where nanotechnology has a huge impact on the textile industry. This article describes current developments in materials for smart nanotextiles and some of the many applications where these innovative textiles are of great benefit

Textile-based wearable sensors for assisting sports performance

There is a need for wearable sensors to assess physiological signals and body kinematics during exercise. Such sensors need to be straightforward to use, and ideally the complete system integrated fully within a garment. This would allow wearers to monitor their progress as they undergo an exercise training programme without the need to attach external devices. This takes physiological monitoring into a more natural setting. By developing textile sensors the intelligence is integrated into a sports garment in an innocuous manner. A number of textile based sensors are presented here that have been integrated into garments for various sports applications

Integrated circuit interface for artificial skins

Artificial sensitive skins are intended to emulate the human skin to improve the skills of robots and machinery in complex unstructured environments. They are basically smart arrays of pressure sensors. As in the case of artificial retinas, one problem to solve is the management of the huge amount of information that such arrays provide, especially if this information should be used by a central processing unit to implement some control algorithms. An approach to manage such information is to increment the signal processing performed close to the sensor in order to extract the useful information and reduce the errors caused by long wires. This paper proposes the use of voltage to frequency converters to implement a quite straightforward analog to digital conversion as front end interface to digital circuitry in a smart tactile sensor. The circuitry commonly implemented to read out the information from a piezoresistive tactile sensor can be modified to turn it into an array of voltage to frequency converters. This is carried out in this paper, where the feasibility of the idea is shown through simulations and its performance is discussed.Gobierno de España TEC2006-12376-C02-01, TEC2006-1572

Integration and embedding of vital signs sensors and other devices into textiles

The development of ubiquitous vital sign monitoring has become a very up-to-date research theme for many academics and industrial companies in the last years. With new materials and integration techniques, it is possible to implement vital sign monitoring in an economic manner, directly into textile products. This unobtrusive presence of sensors is especially important for the monitoring of children or elderly people. This paper focuses on two aspects of sensor integration: Integration of off-the-shelf electronic components, and the use of the textile material itself as sensor, or in general as an electrically active element presenting some exploratory work in the integration of electronic devices into textiles. The main objective was to reproduce and improve on previous work presented by other authors, and foster possibilities of developing garments for vital sign monitoring with immediate industrial and economic feasibility. The use of standard production techniques to produce textile-based sensors, easily integrated into garments and with mass-market potential, is one of the important motivations for this work

Polymer-Based Self-Standing Flexible Strain Sensor

The design and characterization of polymer-based self-standing flexible strain sensors are presented in this work. Properties as lightness and flexibility make them suitable for the measurement of strain in applications related with wearable electronics such as robotics or rehabilitation devices. Several sensors have been fabricated to analyze the influence of size and electrical conductivity on their behavior. Elongation and applied charge were precisely controlled in order to measure different parameters as electrical resistance, gauge factor (GF), hysteresis, and repeatability. The results clearly show the influence of size and electrical conductivity on the gauge factor, but it is also important to point out the necessity of controlling the hysteresis and repeatability of the response for precision-demanding applications

Multimaterial Piezoelectric Fibres

Fibre materials span a broad range of applications ranging from simple textile yarns to complex modern fibre-optic communication systems. Throughout their history, a key premise has remained essentially unchanged: fibres are static devices, incapable of controllably changing their properties over a wide range of frequencies. A number of approaches to realizing time-dependent variations in fibres have emerged, including refractive index modulation1, 2, 3, 4, nonlinear optical mechanisms in silica glass fibres5, 6, 7, 8 and electroactively modulated polymer fibres9. These approaches have been limited primarily because of the inert nature of traditional glassy fibre materials. Here we report the composition of a phase internal to a composite fibre structure that is simultaneously crystalline and non-centrosymmetric. A ferroelectric polymer layer of 30 μm thickness is spatially confined and electrically contacted by internal viscous electrodes and encapsulated in an insulating polymer cladding hundreds of micrometres in diameter. The structure is thermally drawn in its entirety from a macroscopic preform, yielding tens of metres of piezoelectric fibre. The fibres show a piezoelectric response and acoustic transduction from kilohertz to megahertz frequencies. A single-fibre electrically driven device containing a high-quality-factor Fabry–Perot optical resonator and a piezoelectric transducer is fabricated and measured.National Science Foundation (U.S.) (Materials Research Science and Engineering Centers Program, award number DMR-0819762)United States. Defense Advanced Research Projects Agency (Griggs)United States. Army Research Office (Institute for Soldier Nanotechnologies, contract no. W911NF-07-D-0004

Robust adaptive control of conjugated polymer actuators

Conjugated polymers are promising actuation materials for bio and micromanipulation systems, biomimeticrobots, and biomedical devices. Sophisticated electrochemomechanical dynamics in these materials, however,poses significant challenges in ensuring their consistent, robust performance in applications. In this paper aneffective adaptive control strategy is proposed for conjugated polymer actuators. A self-tuning regulator isdesigned based on a simple actuator model, which is obtained through reduction of an infinite-dimensionalphysical model and captures the essential actuation dynamics. The control scheme is made robust againstunmodeled dynamics and measurement noises with parameter projection, which forces the parameter estimates tostay within physically-meaningful regions. The robust adaptive control method is applied to a trilayer polypyrroleactuator that demonstrates significant time-varying actuation behavior in air due to the solvent evaporation.Experimental results show that, during four-hour continuous operation, the proposed scheme delivers consistenttracking performance with the normalized tracking error decreasing from 11% to 7%, while the error increasesfrom 7% to 28% and to 50% under a PID controller and a fixed model-following controller, respectively. In themean time the control effort under the robust adaptive control scheme is much less than that under PID, whichis important for prolonging the lifetime of the actuator

The Effect of Tensile Hysteresis and Contact Resistance on the Performance of Strain-Resistant Elastic-Conductive Webbing

To use e-textiles as a strain-resistance sensor they need to be both elastic and conductive. Three kinds of elastic-conductive webbings, including flat, tubular, and belt webbings, made of Lycra fiber and carbon coated polyamide fiber, were used in this study. The strain-resistance properties of the webbings were evaluated in stretch-recovery tests and measured within 30% strain. It was found that tensile hysteresis and contact resistance significantly influence the tensile elasticity and the resistance sensitivity of the webbings. The results showed that the webbing structure definitely contributes to the tensile hysteresis and contact resistance. The smaller the friction is among the yarns in the belt webbing, the smaller the tensile hysteresis loss. However the close proximity of the conductive yarns in flat and tubular webbings results in a lower contact resistance