It is not only in summer that it can get hot during sports activities, because sport during winter also has its pitfalls. Outside it is freezing cold, and insulating clothing is a must. However, if you move around a lot, your body’s own “AC” kicks in: The skin releases liters of cooling sweat. To ensure that we don’t freeze in our wet clothes during our well-earned breaks, Empa researchers, in collaboration with industrial partners, have developed an electro-osmotic membrane, which keeps clothing (and the athlete) dry and thus warm. The Swiss high-end sportswear company KJUS has integrated the technology into a ski jacket that can be operated by a smartphone. In experiments in Empa’s climate chamber, the researchers also conﬁrmed the functionality and wearing comfort of the jacket with a “pump effect”.
Avatar with suit and tie
Whether jackets and pants are comfortable to wear and release body heat effectively is now predictable thanks to virtual modeling. Empa scientist Agnes Psikuta and her team from the “Biomimetic Membranes and Textiles” lab in St. Gallen have developed software that takes into account fabric characteristics, the body physique and insulating air cushions between skin and clothing. “Using an anatomically customizable avatar, it is possible to simulate how an item of clothing ﬁts perfectly on the body and what thermal effects it has, even when the person is moving,” explains Psikuta. Thus, a design for a suit can be optimized on the avatar before it is sewn from actual fabric.
But there are also suits whose wearers have to protect themselves from extreme external conditions: The protective clothing of ﬁreﬁghters must be thermally insulating, ﬁre- and waterproof as well as breathable, but at the same time neither too heavy nor inﬂexible. Insulating air cushions are, therefore, crucial. Such protective clothing can be optimized in the lab by means of anatomical manikins. “In near-reality experiments, we can ﬁnd out how the insulation in a protective suit changes depending on whether the wearer is aiming the ﬁre hose at the ﬁre while kneeling or crawling on his knees through a burning building,” says Psikuta.
Foot sensor for athletes
Movement is also the focus of a “garment” designed based on wood: Within the D-Sense project, a ﬂexible joint sensor made of nanocellulose is being developed. The 3D printed sensor based on renewable resources is biocompatible and lies directly on the skin. It is electrically conductive because the nanocellulose “ink” is combined with silver nanowires during the 3D printing process. When worn as an insole, for example, in the sneaker of a professional athlete, the sensor measures, among other things, load, pressure and the effect of force, so that the movement of the joints can be precisely analyzed. “Because of its mechanical properties, nanocellulose is particularly well suited for creating new composite materials,” says Gustav Nyström, head of Empa’s “Cellulose & Wood Materials” lab in Dübendorf. The multilayer sensor is, therefore, one of the projects within the ETH Domain’s Strategic Focus Area “Advanced Manufacturing”. The application of such a joint sensor could also be used in future in patients with joint implants in order to accompany the optimal healing process.
Data analysis while sleeping
Other high-tech garments are also ideal for use in state-of-the-art medicine. For instance, even when we are seemingly immobile, say, when we sleep, numerous muscles are active: The heart beats ceaselessly, and the chest rises and falls. But how does the heart beat during sleep? And does our breathing pause, or does it ﬂow calmly and steadily through the night? Empa researchers have developed a cardio belt, which, thanks to embroidered electrodes, can register heart activity throughout the night. Using the Empa plasma coating facility, nanometer-thin metallic layers were applied to the threads, making them conductive, skin-friendly and washable. The ﬂexible measuring device is used, for example, for people who suffer from respiratory arrest during sleep, so-called sleep apnea. Further clinical applications of the sensor belt are currently being developed with partners from industry and the medical sector. For example, the ECG belt – complemented by sensor technology for measuring body temperature – is intended to support the diagnosis of dementia such as Alzheimer’s, since the long-term measurement of vital parameters can provide information on cognitive performance.
Together with researchers from the Université de Haute-Alsace in Mulhouse, Empa researchers are also working on equipping textiles with additional sensors. In this way, the range of applications in medicine and sports and the wear comfort can be extended even further. “We will equip a piece of clothing, such as a T-shirt, with sensors for the analysis of various health parameters,” says Simon Annaheim. The core element for the measurement of other parameters such as respiratory rate or oxygen saturation are optical polymer ﬁbers produced by melt spinning.
Camouflage for artificial heart pumps
Since the micro-design of textile ﬁbers can be precisely controlled by various spinning processes, Empa researchers are also developing membranes that resemble biological tissues. For example, polymer membranes made of highly elastic core-sheath ﬁbers are colonized with human cells so that a multi-layered, functional tissue can grow. This research is part of the “Zurich Heart” project, on which Empa is working together with the University of Zurich, ETH Zurich and Zurich University Hospital. The “living” membranes are intended to line the inner surface of artiﬁcial heart pumps as “camouﬂage”, so that the body can better tolerate the device and malfunctions can be avoided.
Medication to wear
Textile ﬁbers can also be used in the form of “intelligent” wound dressings to indicate a disturbed healing process in complex wounds at an early stage. Moreover, they can release substances such as antibiotics, painkillers or natural remedies. To ensure the dosage of these active ingredients is precise, the researchers have devised a tricky control mechanism: A slight pressure on the wound dressing or a light signal controls the release of the medication. Chemical stimuli from the patient, such as the altered pH value of a wound, can also trigger drug delivery.
Polymer ﬁbers can also be processed into sensors to detect volatile substances in our breath. Luciano Boesel’s team uses electrospinning technology to produce multilayered polymer membranes that are designed to “sniff out” certain gases in human breath. “Volatile amines are formed during bacterial infections such as pneumonia or chronic kidney disease,” says Boesel. His team is now developing a highly sensitive amine sensor that will detect traces of different amines in the breath in order to diagnose diseases as early and non-invasively as possible.
Nanobags for active ingredients
Amin Sadeghpour is exploring the micro- and nanostructure of our clothing even more deeply. He is constructing tiny nanocubes that resemble a cell membrane. With a side length of around 10 nanometers, the cubes hold only the tiniest amounts of active ingredients. However, thanks to their construction from small tubes, it is possible to package different substances together that would normally not be mixable. This is ideal for combining several drugs or vitamins. The biocompatible cubes are grouped together in “nanobags”, so-called cubosomes. In the electrospinning process, they can be attached to ﬁbers with which wound dressings or “caring textiles” can be produced. These nanoelements, biocompatible materials and smart ﬁbers will in future be used to produce garments that not only perfectly ﬁt our avatars, but also lead to top performance in sports and medical practice.