Heart-lung machines are used to support heart surgery and acute lung failure. So-called oxygenerators, often using membrane technology, ensure gas exchange in the blood. The STFI has now developed a novel manufacturing process for multiaxial mat structures that enable gas exchange. The aim of the research project was to develop a multiaxial mat structure made of hollow filament membranes as well as the necessary manufacturing technology. The result of the development is a textile structure in which diagonally laid weft threads of hollow filament membranes are bound at the intersections of stitch-forming yarns.

Using a special diagonal laying device, it was possible to set the desired angle of the hollow filaments by means of weft insertion in line with the stitch sequence without damaging the membranes. A right/left crochet galloon knitting machine was optimised for the implementation. In addition to making adjustments to the knitting point, the researchers at STFI developed a new yarn feed system using a rotating circular creel and implemented it in the knitting process. For processing, it was also necessary to check all elements in contact with the sensitive hollow filament membranes and replace them with low-friction elements in individual cases.

After optimising the machine, a multiaxial mat structure could be produced from the sensitive hollow filament membranes. Textile-physical and laboratory tests confirmed the suitability of the developed mat.

Dipl.-Phys. Nadine Liebig
Technical woven and knitted fabrics
+49 371 5274-271
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Nanofibre layers are ideal barrier materials. Due to their particularly fine structure, nanofibres offer a better barrier against bacteria and viruses than, for example, a meltblown or spunbond nonwoven, which is why they can be used in combination with nonwovens as a filter material in face masks or as a barrier material in protective suits. The use of nanofibres as single fibre layers has not yet been realised. Nanofibre layers have low mechanical stability and are therefore combined with macroscale substrates and cover materials. The challenge is to achieve sufficient adhesion between the individual layers and to maintain the positive properties of the nanofibres.

The aim of the NanoHyb research project was to develop innovative hybrid nonwoven structures with an integrated nanofibre layer. Meltblown nonwovens were developed as the carrier and top layer. The nanofibre layer was produced by an electrospinning process. Composite structures were developed from the individual layers. According to the state of the art, the layers are usually bonded using adhesives. In order to ensure the adhesion of the individual layers without the use of a bonding agent, the possibility of plasma modification or laser bonding was investigated. Pandemic protection in the form of disposable protective and clothing textiles was considered as a possible end application. For such applications, the treatment of the novel hybrid structures with antimicrobial or antiviral agents was analysed and evaluated.

The desired requirements for the materials to be developed were achieved in the project. Meltblown nonwovens with filament diameters < 700 nm were produced, combined with nanofibre layers and successfully joined using an innovative laser transmission welding process.

Dr. rer. nat. Anna Große
International Cooperation I Transfer
+49 371 5274-282
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Twisting an ankle in dynamic sports with rapid changes of direction, such as volleyball, basketball or badminton, is a common cause of ankle injuries. The orthotic devices currently available on the market significantly restrict movement and some are not suitable for wearing in shoes. The market therefore lacks a system that allows full freedom of movement of the ankle joint and at the same time protects against twisting to prevent injuries.

Researchers at STFI and Ruprecht-Karls-Universität Heidelberg are working with industry partners to develop supports and compression stockings with integrated stretch-stiffening elements. Stretch-stiffening structures allow moderate stretching up to a critical resistance. Once the critical point is reached, the structure stiffens and blocks further movement. By changing the geometry of the structures, the point of material stiffening can be adapted to the human anatomy. At Ruprecht-Karls-Universität, these special structures were applied to knitted fabrics using 3D printing. After testing various materials, thermoplastic polyurethane proved to be the most suitable. The best possible adhesion of the print to the knitted fabrics produced by Strumpfwerk Lindner GmbH was also a central part of the investigations. Significantly better adhesion was found on the bandage material than on the compression stocking material.

Similar structures have been produced at the STFI using textile manufacturing processes. However, the desired strain-stiffening effect could not be achieved. On the other hand, the use of flat knitting technology resulted in patterns that exhibited similar behaviour to the 3D printed structures in the tensile test. Although the knitted patterns alone are not sufficient to withstand the forces that occur during twisting, they are suitable for covering and supporting the 3D-printed structures. The functionality of the foot is tested on a test stand developed by Ruprecht Karls University. However, tests on wearing comfort are planned at Orthopädie-Technik Wolf GmbH.

Jenny Liebelt, M. Sc.
Technical woven and knitted fabrics
+49 371 5274-279
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Research project AktiSup (Handout)

Perfluorinated organic compounds, or PFCs, are valued for their water-, grease- and dirt-repellent properties. They make workwear and outdoor clothing weatherproof, for example, but pose a high health risk if they evaporate or are washed out. STFI has added an analyser from a1-environsciences GmbH, Düsseldorf, to its range for testing organically bound fluorine and halogens in general. Combustion ion chromatography (C-IC) is a system that combines a high-temperature combustion/digestion unit with downstream ion chromatography (IC). This allows samples to be analysed safely, reproducibly, selectively and with sufficient sensitivity for the presence of organically bound fluorine or halogens in general.

The instrument thus provides an elegant method for the complete degradation of samples and the quantitative determination of the halogens present. In practice, the AOF or AOX value (AOX = adsorbable organically bound halogens) is obtained. Both liquid and solid samples can be analysed. The total halogen content is determined. Currently, the determination of fluorine is preferred as it is difficult to access by other analytical methods.

Dr. rer. nat. Antje Melzer
Accredited Test Lab
+49 371 5274-210
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Textile chemical and human ecological testing of the Accredited Test Lab

Communicating with people who have severe multiple disabilities is a major challenge for carers. Due to a lack of time, carers often focus on medical aspects, which can increase the social isolation of those affected and affect their wellbeing. Functional textiles offer an innovative solution. They create new opportunities for interaction and communication while meeting the high demands of the intended applications.

One project has driven forward the development and integration of electrically conductive materials in elastic textiles. The aim was to develop intelligent, stretchable surfaces that could be used in particular in music therapy for people with severe multiple disabilities.

During the project, specific profiles for sensor and textile parameters were created and suitable materials were integrated into elastic textile structures. The resulting knitted surfaces, which have multi-part, electrically conductive and stretchable structures, were tested specifically for use in music therapy. Their functional properties and resilience were tested after mechanical stress and washing processes. The results of the project are smart textiles specifically tailored to the needs of disabled people and provide important insights for future applications in the field of smart textiles.

The results include functional prototypes of electronic hardware combined with robust, sensitive arm warmers in different sizes.

Dipl.-Ing. (FH) Frank Weigand
Technical woven and knitted fabrics
+49 371 5274-226
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Research project TexgAT (Handout)

On the evening of 4 September 2024, the annual company race took place in Chemnitz. More than 10,500 runners, among them 15 from the STFI, took part in the 4.8 kilometre race. Team Raupe, as the STFI runners are called after their former running mascot Andi the caterpillar, had a lot of fun in the hot summer temperatures. Starting in Neumarkt, the teams set off in waves around the beautiful pond called Schlossteich and back into the city centre. It was a relief to cool off at the finish line.

It was a great event and we would like to take this opportunity to thank all the participants and supporters as well as the STFI Ideenwerkstatt for organising the participation at this event.