From the Sector

According to the World Health Organization (WHO), cardiovascular disease is one of the most common natural causes of death. Every year, it is the cause of death of around 17 million people worldwide. The Peter Dornier Foundation Prize 2022 has now awarded a research work that is to improve the medical care of people with insufficient heart valve function in the future and prolong the patients' lives.

The human heart is a high-performance machine: over the course of a person's life, it beats almost three billion times, pumping around 200 million litres of blood through the body. Enormous stresses that can sometimes lead to life-threatening signs of wear and tear. If a heart valve gets out of step, patients usually get artificial-mechanical or biological valves as a replacement. However, mechanical solutions imply patients to take blood-thinning medication for the rest of their lives. In addition, there may be audible closing noises. For example, almost a quarter of patients with mechanical heart valves complain of sleep disturbances. Biological heart valves, on the other hand, such as those made from animal tissue, require a great deal of manual work and have a shorter lifetime.

Potential of weaving for medical products demonstrated
For this reason, Graduate Engineer Mathis Bruns at the Institute for Textile Machinery and High-Performance Textile Materials Technology (ITM) at the TU Dresden is researching an implant alternative made of fabric. As part of a research project that also involved heart surgeons from the Dresden Heart Centre and the University Hospital in Würzburg, Mr. Bruns provided important findings for weaving an artificial heart valve in his diploma thesis. For his work entitled "Development of tubular structures with integrated valve function", Mathis Bruns has now received the Peter Dornier Foundation Prize 2022, endowed with 5,000 euros. In his laudation, Dr. Adnan Wahhoud, former head of the development department of air-jet weaving machines at DORNIER in Lindau, said: "With his work, the winner of the award demonstrates very clearly the potential of weaving technology to produce fabrics of complex form, geometry and structure with the aim of prolonging and improving people's lives." The award-winning thesis enriches research into three-dimensional tissues for use in medicine.

Weaving replacement heart valves without seams
"A particular advantage of our approach is the integral production method", says foundation prize winner Mathis Bruns. “The geometry and function of a heart valve is that complex that woven heart valves could not be produced in this form previously. Through the combined use of a rigid rapier weaving machine with bobbin shield and a Jacquard machine, it is possible to weave the replacement heart valve in such a way that it no longer has be sewn together. Even the tubular structures for the blood vessels and the integrated valve function are ‘all of one piece’. Seams are always a weak point in textile medical products," Mr. Bruns adds. “Another advantage of the woven heart valve is the possibility to insert it by the help of minimally invasive surgery. Hence, the folded valve which is about the size of a tea light is to be pushed with a catheter via the bloodstream to the target position in the heart and unfolded there. The patient's chest and heart would then no longer have to be cut open”, explains prize winner Mr. Bruns.

Textile structure is similar to human tissue
A wide variety of medical products have always been produced on DORNIER weaving machines. Customers use them to produce fabrics for bandages, prostheses, blood filters and orthoses among other things. For Mathis Bruns, it is only evident that implants such as heart valves will more and more be woven on the machines from Lindau in the future. "Textile tissue is very similar to human tissue," he says. The human body consists largely of thread-like materials, just as a textile fabric is made up of thousands of individual threads. "Muscle fibres convey force impulses, nerve tracts send stimuli such as pain and brain cells convey information via thread-like dendrites and axons." Because of their ‘thread-like properties’, woven implants are therefore particularly suitable for medical applications.

Kai-Chieh Kuo, PhD student at the Institut für Textiltechnik (ITA) of RWTH Aachen University, was awarded the German Textile Mechanical Engineering 2021 Best Master's Thesis Award for his master's thesis entitled "Modification of the tube weaving process of fine yarns for the production of woven ultra-low profile stent grafts". The prize is endowed with 3,500€. Peter D. Dornier, Chairman of the Board of the Walter Reiners-Stiftung (Foundation), virtually presented the award on the occasion of the ADD International Textile Conference on 9 November 2021.

Minimally invasive endovascular aortic repair (EVAR) with textile stent-graft systems is nowadays a clinically established therapy procedure for the treatment of abdominal aortic aneurysms (AAA) – pathological bulges of the aorta. Due to the thick profile of the folded stent graft systems, there is currently a high risk of injuring narrowed or highly angulated access vessels from the inside during implantation. Stent graft systems with smaller profiles could provide an improvement, which could overcome complicated access routes through a lower bending stiffness. One possible approach for reducing the system profiles is the use of thin-walled tubular woven fabrics made of ultrafine multifilament yarns (≤20 dtex) as graft material.

Up to now, it has not been possible to process the fine yarns with the required high thread density (>200 threads/cm) and the available weaving technology in order to guarantee sufficient tightness against blood.

In his master's thesis, Kai-Chieh Kuo made high-density tubular weaving of ultra-fine filament yarns possible for the first time by means of suitable modifications to a shuttle loom as well as adaptations in the weaving preparation. In particular, he developed a new innovative reed technology that reduces warp thread friction during the shedding process and thus improves the process stability of the dense tube weaving process of fine yarns.

With the help of the process modification, it was then possible to produce high-density, thin-walled tubular woven fabrics, which were positively evaluated with regard to their suitability for a stent graft. Above all the potential of these tubular fabrics lies in their extremely thin-walled fabric profile, which seals well against blood. By using these new types of tubular fabrics as graft material for stent grafts, the system profile of the folded stent graft system can be reduced without having to compromise the blood tightness of the implant. The technology developed by Mr Kuo is not only applicable to stent graft systems, but also offers great possibilities for use in all other endovascular implants such as trans catheter heart valves, covered stents and small-lumen vascular prostheses.