Emerging Technologies and Research in Electronic Textiles

The continued interest and growth in wearable and soft electronics devices have synergistically ushered in an entirely new area of innovative research and commercialization of e-textile products. Systems/devices in this category include multifunctional fibers and textiles with electronic capabilities having potential applications ranging from weapon systems to everyday textiles. The underlying science and technology of e-textiles are intertwined with many new and emerging fields such as nanotechnology, biomimetics, molecular electronics, etc. In this presentation, the general area of e-textiles will be introduced with an overview of the current state of the art and the challenges. More importantly, the presentation will focus on the complex challenges posed by the need for collaborative research in e-textiles involving multiple disciplines. The subsequent discussion will focus on the continuing effort at the SMARTextiles laboratory at N.C. State University to seamlessly integrate electronic functionalities directly into fibers and textiles to develop electrical devices such as sensors and actuators. In one of our ongoing research, tricomponent melt extrusion is being used to produce sensory fibers [1,2]. Once woven into a fabric, the fibers can be used as a sensor array to detect pressure, moisture, etc. In another research, an easy-to-manufacture, tunable, fully-textile sensor system that can detect pressure, humidity, or wetness is being studied [3,4]. Here capacitive pressure sensors are formed via a traditional sewing process with commercially available conductive sewing yarns. In both cases, the simple sensor design using conventional fabrication techniques resulted in practical and scalable methods of producing textile-based sensory arrays. The relationship between the sensor's physical, mechanical, and electromechanical properties, including hysteresis and sensory response, will be discussed. In addition to sensors, actuators are also essential for many e-textile applications. Therefore, we are exploring the movement and morphing in biological systems to develop advanced flexible structures [5]. For example, the nastic motion of plants in response to environmental stimuli, e.g., the rapid closure of the Venus flytrap's leaves, utilizes snap-through instabilities originating from the anisotropic deformation of plant tissues. In contrast, ballistic tongue projection of chameleon is attributed to direct mechanical energy transformation by stretching elastic tissues in advance of rapid projection to achieve higher speed and power output. We have developed a bistable all-polymer laminate containing dielectric elastomers, which double as both structural and active materials. The electrical actuation of bistable structures obviates the need for continuous application of electric field to sustain their transformed state. The experimental results are qualitatively consistent with our theoretical analyses of prestrain-dependent shape and bistability. We are currently exploring similar fiber-based structures for textile applications.