TEXTILES.ORG
Exciting developments highlight new applications for technical textiles and nonwovens.
By Marie O’Mahony
Universities and research institutions all over the world are progressing with innovative and notable developments in medical and “well-being” products and applications, with research ranging from a tissue-engineered heart valve to a smart energy-efficient architecture membrane based on the skin of a polar bear. The recent biannual Techtextil trade fair in Frankfurt, Germany, offered participants the opportunity to demonstrate research, engage in dialogue and develop new relationships within the specialty fabrics industry worldwide.
Usability at the core
The Textile Research Institute Thuringia-Vogtland (TITV) in Greiz, Germany, demonstrated how quickly developments are occurring in conductive textiles. Just two years ago, they were showing smart diagnostic developments for medical applications that were incorporated individually using different processes—all of which increased production time and cost. Today, new manufacturing technology developed in collaboration with the Tajima embroidery machine (from Japan-based Tajima Group) allows for automated assembly. The process takes a conductive yarn and embroiders it onto the fabric with LEDs that are machine-picked from their box, positioned with a conductive glue and then secured using laser or hot-air soldering.
Running the Tajima machine, TITV demonstrated the speed and refinement of the process and the finished quality. Researcher Dirk Zschenderlein presented a co-authored paper titled “Interconnection techniques to connect textile substrates and electronic components,” which discussed the range of interconnections using conductive thread currently in use, from crimping and piercing to Velcro™, press studs and embroidery, while focusing on comfort, appearance, tactility and usability. (It’s pointless to have a high-performing device if the user doesn’t use it or uses it incorrectly.)
The Swedish School of Textiles continues to focus on medical research as interest in and demand for textiles in medical applications grows. Post-operation scar tissue is a problem faced by an estimated 30 percent of heart bypass patients within a year of surgery; this can result in further blockage of blood vessels, leading to decreased blood flow and the formation of a blood clot. In developing y-graft, researchers Erney Mattsson and Torbjorn Lundh created a unique solution in their design of a knitted stent that can literally be undone: The stent remains in the body only as long as it is needed. Once it has served its purpose, it is pulled out. This is less invasive on the body and decreases the risk of formation of scar tissue.
In another development, a piezoelectric biocomponent fiber is used to allow for more discrete sensors to be worn next to the body. Ph.D. student Erik Nilsson demonstrated the use of the fiber in a narrow weave in which crystallized polyvinylidene fluoride (PVDF) nanofibers are given piezoelectric and pyroelectric properties and function as a sensor, with the potential to be used for cardio-respiratory monitoring during sleep. The design takes into account the importance of wearability, comfort and minimizing bulk. Breathing on the narrow fabric—a truly smart material— Nilsson demonstrated the speed and accuracy of the technology in gathering and relaying data.
Smart materials and systems have also been developed by researchers at the University of Ghent in Belgium. As part of a research program on color-changing materials, researchers use halochromic dyes in wound dressings to give a visual diagnostic of a patient’s pH balance. By incorporating the technology into a textile substrate, flexibility, breathability and patient comfort are all taken into account. Researchers are pursuing a wide range of smart material and design for applications in health and well-being, including a wearable obstacle detection system for the visually impaired.
Building the future
Textiles in architecture and construction are also becoming a strong focus of research among a number of universities. Two distinct fields were evident at the show: The first relates to architecture membranes and the second, textile reinforcement of concrete. Biomimetics, or biomimicry, is the extraction of good design from nature. Velcro™, based on the ability of burrs to attach themselves to the fur of a passing animal, is an early example of this process, which employs both design and engineering skills.
This area is attracting a lot of attention but is currently lacking in strong realized design and applications. It was especially welcome, then, to see the design principles applied and showcased by the “Polar Bear Pavilion” from Dr. Jamal Sarsour at ITV, Denkendorf, Germany.
The design addresses the need for better temperature control in architectural membranes. In nature, the polar bear has the ability to gather and store heat using its densely packed colorless fur, then absorbing and storing the heat in its black skin. In the architecture membrane, a spacer fabric is used. The base layer of the knitted fabric is black, and the outer layer and perpendicular yarns are all transparent. The university designed and constructed a building to demonstrate how the technology works. The outer layer forms radiolucent insulation that houses an air-transport layer followed by an absorber layer that is heated by the radiation. Thermochemical technology forms the basis of the energy storage unit that works by means of moisture exchange. (For more on this technology, see “Future Textiles” in the June 2013 Review.)
One reason for the success of this idea is that the researchers have acknowledged the potential as well as the limitations of biomimetics. The idea that the fabric alone could capture, store and release energy is exciting but isn’t feasible using current technologies. Embracing the need for a separate energy storage unit has meant that the design can be realized and the concept progressed. The hope is that other researchers working in the field will take this as a good example of when to combine design approaches.
Concrete examples
Researchers at Techische Universitat (TU) Dresden and RWTH Aachen University presented two approaches to the textile reinforcement of concrete. The Dresden paper, “Textile Reinforced Concrete: Practical Applications” (M. Lieboldt, F. Schladitz and M. Curbach), began with a history and reminder of early engineers’ interest in textile reinforcement of buildings with an 1881 patent from Joseph Monier in Paris. The focus was on contemporary developments and issues—particularly in restoration work such as the preservation of the historical barrel vault in Zwickau, Germany, built in 1903. Planning and preservation requirements stipulated that the geometry of the shell should be maintained. The solution: the use of carbon-fiber reinforcement with a very fine layer of concrete sprayed over it, minimizing the amount of additional material needed.
In the presentation “Applications for textile-reinforced concrete: Requirements for inherently stable textile reinforcements” (C. Kulas, Prof. Dr. J. Hegger and Dr. N. Will), RWTH Aachen and IMB, researchers clearly and simply pointed out the benefits to TRC, which include reduced weight, reduced transport costs, economic benefit and ecological building techniques. Manufacturing involves a number of steps, from making the textile to placing and fixing it in the mold and in the oven to cure. All of this involves human intervention; one of the key activities identified for future work is addressing how the production of intersections can be automated. Whether this level of automation can be achieved remains to be seen.
Many of the industry partners for university research also exhibited at the show, and it was interesting to see how this work relates to their overall businesses. While European Union (EU) funding certainly helps facilitate these relationships, they are primarily driven by a common purpose and goal in resolving clearly defined problems or needs in the marketplace. It was noticeable that the universities were all European. There is some excellent research happening in the Americas and Asia, and it would be wonderful to see more representation from these regions in the future. It’s exciting to see these developments showcased, and for dialogue to grow to help progress and innovation continue across the industry worldwide.