Anemone Seger — 22.08.2017

In the "Subitex" research initiative, the Swiss textile federation Swiss Textiles and the textiles research laboratory at Empa are working together to promote innovation. Ten CTI projects have already been initiated.

"When people hear the term textiles", very few immediately think of textile sensors, heart pumps or plasters that can dispense substances. But the notion that, when we speak of textiles, we are referring to woollen socks or cotton shirts, is well and truly outdated, explains Prof. Dr. René Rossi, head of the Laboratory for Biomimetic Membranes and Textiles at Empa (Swiss Federal Laboratories for Materials Science and Technology) in St.Gallen. His laboratory is focusing on the development of materials – especially textiles – that protect the human body and enhance its performance. "We speak of a textile when a one-dimensional material, i.e. a fibre, is processed into a twoor three-dimensional object."

Every material can be turned into fibres, and thus into a textile, including ceramics, wood, metal, plastic or cotton. Textiles have enormous potential thanks to their specific properties. Most of them are flexible, light, tough, pliable but dimensionally stable and have a large surface area. No other material possesses these properties.

Prof. Dr. René Rossi is head of the Subitex project at Empa.

Subitex – Sustainable Biomedicine Textiles

The textiles and clothing industry has a lengthy tradition in Switzerland, which for many years was a leader in the areas of embroidery and light cotton fabrics. But if Swiss textiles companies are to remain internationally competitive, they will have to be innovative. And this is where the "Subitex – Sustainable Biomedicine Textiles" research initiative comes in, which was launched at the beginning of 2015 by industry association Swiss Textiles in cooperation with Empa in St.Gallen. Here, industry and research are joining forces to promote innovation through knowledge transfer and bring the resulting products more quickly onto the market. "In the field of biomedicine, textiles offer enormous potential for use inside as well as outside the body, and this has to be more effectively exploited," explains Rossi, who is head of the Subitex project at Empa. Here I am thinking of textile sensors, for example, or plasters for the targeted delivery of medicaments. The main sponsor of Subitex is Swiss Textiles, which is providing its members with this exclusive form of cooperation – 15 of its members are currently involved in the project. "With this initiative, the Swiss textiles industry is underscoring the importance of textile research, while Empa has undertaken to pursue this field of research for a further five years," notes Rossi. Subitex can already boast initial successes, just two years after its inception: it has resulted in ten projects that are being co-financed by the Federal Commission for Technology and Innovation (CTI) and which involve the following companies:

Flawa AG, AG Cilander, E. Schellenberg Textildruck AG, Mammut Sports Group AG, Schoeller Textil AG, Serge Ferrari Tersuisse AG and TISCA Tischhauser & Co. AG. For patent protection reasons, none of the companies want to commentat present on the content of these CTI projects. Subitex is a five-year research programme.

Empa research team with Dr. Giuseppino Fortunato (second from right), who is involved in the Zurich Heart project. There are two team members missing on the picture.
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Empa’s entire textile know-how is flowing into the industry

How does the cooperation between the industry and Empa function? "It’s a push-and-pull process, i.e. we at Empa are pushing innovation in the industry by implementing ideas that evolve from our research together with a Subitex partner, and, in turn, companies are able to obtain our support for their ideas or products," explains Rossi. Empa organises two innovation workshops each year for Subitex partners, at which three researchers present new technologies and/or materials. The companies in attendance can then hold individual discussions with the researchers. "At these workshops, Empa is successively placing its entire textile know-how at the disposal of the participating companies," says Rossi.

In order to pass on even more know-how to its Subitex partners, Empa has invested a portion of the financial support for Subitex into the "Self-care materials" programme of the Competence Centre for Materials Science and Technology" (CCMX) at the ETH Domain. This programme is researching fibre structures for the delivery or absorption of substances. It entails a combination of basic and industrial research and is lucrative in that the Swiss National Science Foundation (SNSF) is providing the same amount of funding as the industry.

Prof. Dr. René Rossi, Empa

Every material can be turned into fibres, and thus into a textile.
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Human body as a textile

The "Zurich Heart" project is a prime example of the direction in which textile research is heading in the field of biomedicine: heart pumps are being developed that one day will minimise the need for donor hearts. This project involves cooperation between the Federal Institute of Technology, Zurich, the University of Zurich and the Zurich University Hospitals, the "Deutsches Herzzentrum" in Berlin and Empa.

Artificial heart pumps have been in use for around 30 years, but they can cause blood clots because the blood comes into contact with an exogenous material. To prevent this, the patient’s own cells need to be cultivated on the interior surface of the Zurich Heart pump. And this is where Empa’s textile research comes in.

The researchers aim to emulate the structure of a blood vessel in the interior of the pump. Viewed from the interior outwards, blood vessels comprise a layer of endothelial cells, muscle cells and an extracellular matrix (or scaffold) that holds the cells together. "In the Zurich Heart, this extracellular matrix is replaced by a polymeric fleece," explains Dr. Giuseppino Fortunato, a researcher in the Zurich Heart project team at Empa. "The principle here is for the fleece to be spun with a layer of the patient’s own muscle cells and to subsequently cultivate a layer of endothelial cells."

A team of eight biologists, chemists and physicists from Empa are currently involved in this research project, in which the focus is on two central issues: how the fleece can be spun using muscle cells and how the elastic material can be firmly attached to the interior of the heart pump.

Dr. Giuseppino Fortunato, Empa

The principle here is for the fleece to be spun with a layer of the patient’s own muscle cells and to subsequently cultivate a layer of endothelial cells.
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Fleece – seven times lighter than copying paper

Fleece comprises continuous or cut fibres in a nonoriented form and without interweaving. In other words, it does not have a regular structure. Under the microscope it resembles an unrolled ball of wool. The fleece for the Zurich Heart consists of fibres that are several hundred nanometres thick and are made from a polymer solution. By way of comparison, the fibres are around 200 times thinner than a human hair.

The fleece is spun using the electrospinning method. Here the polymer solution is placed in a syringe and connected to a high-voltage power supply. The electrical field causes a jet to be formed, and the fibres are swirled and then separated onto a counter-electrode where the fleece is formed. At the same time, the Empa researchers spray the fleece with muscle cells as it is formed so that the latter become embedded in it. "We have already succeeded in producing the fleece and spraying it with cells," says Fortunato, "and are now studying how blood reacts when it comes into contact with the fleece and cells."

Optimal solution: fleece comprising two different materials?

The material that is used for producing the fleece is a decisive factor, because the fleece has to meet a variety of requirements: For example, it has to remain intact inside the pump, it needs to be elastic so that it follows the pump movements, and it has to adhere to the silicon surface of the pump with the aid of a chemical bonding agent. The researchers at Empa are currently trying to identify the most suitable polymer for this purpose: "We can envisage the possibility of obtaining a gradient in the fleece by spinning it with two polymer solutions. In this way, one polymer would be more suitable for the chemical bonding with the pump surface, while the other could be used for securing the optimal interactions with the muscle cells," explains Fortunato. "This could be compared to knitting something using red thread to begin with, then changing to blue halfway through." The researchers anticipate that it will take another ten years or so before this technology can be brought onto the market.

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