Many products that come into contact with the skin, such as medical devices, artificial grass and sports clothing, undergo extensive testing to find out how they affect the skin. Currently, tests involving friction are still conducted in vivo or ex vivo — in other words, using live subjects or areas of skin that have been removed by experimenting with individuals or by using excised human skin removed after surgery. But this kind of testing involves all kinds of ethical and practical difficulties. The industry urgently needs an alternative, such as the artificial skin developed by Morales Hurtado. In the future, the synthetic skin can be used in the sliding tests carried out by FIFA and UEFA, which are performed at the National Sports Centre in Papendal.
Morales Hurtado has developed a double-layer synthetic skin model which tribo-mechanical performance is similar to the real skin. ‘The mechanical behaviour of the synthetic skin — its physico-chemical properties of the model surface, tribology, elasticity and hydration — all correspond very closely to real skin,’ says Morales Hurtado. ‘I compared the synthetic skin with real skin samples from the Radboud UMC, which was also a partner in the project. The synthetic skin consists of two layers. Because of the two layers, the elastic modulus of the model varies as a power law function of the applied force similarly, as the human skin does. At lower forces, the modulus of elasticity is close to that of the stratum corneum. At high forces it gets closer to the values of dermis. The upper layer consists of a thin film (150-200 micrometres thick) using a mixture of synthesized Poly Vinyl Alcohol, rapeseed oil and glutaraldehyde. The lower layer is thicker (1.2mm thick) and has ultra-soft mechanical properties. The artificial skin also adapts to humid conditions. This is the first time that we have been able to replicate this.’
New Measurement Technique
As part of the project, Radboud UMC has developed a non-invasive method for measuring skin damage caused by sliding across another surface. Cell biologist Peter van Erp is very enthusiastic about the research project. ‘Now that it is possible to assess the effects on skin in a quick, reliable and non-invasive way, we’ll be able to determine the effect of sliding across artificial grass more accurately, for example. Does skin turn red because of the heat generated by friction? Do the materials used cause skin irritation, or might they trigger an allergic reaction? Now, we will be able to demonstrate this objectively, because the number of immune cells in the skin would increase significantly. This project has brought us much closer to developing new quality requirements for artificial grass and sports flooring.’
Investment of €7 Million
The artificial skin research is part of the project entitled ‘New Business for Enhanced Skin Comfort’. This is a joint project involving TenCate, the University of Twente, Surface Technology and Tribology, DelTecMetaalMaatwerk, Descol Plastic Chemie BV, Reden BV, the Institute for Sports Facilities BV (ISA Sport), the Agricultural Research Service Foundation, Food & Biobased Research, GreenGran BV, Philips Consumer Lifestyle BV, API Institute and the Department of Dermatology at the UMC St. Radboud. The project was established with assistance from the East Netherlands Development Agency and Innovatieplatform Twente, and was sponsored by the Ministry of Economic Affairs and the provinces of Gelderland and Overijssel. The 11 participating parties from the east of the Netherlands will together be investing €4 million euros over the next three years. Central government and the provinces of Gelderland and Overijssel will also provide a further €3 million for the project.