Empa develops paradoxical tissue

For its material, Empa worked with the so-called auxetic effect, which also occurs in nature, according to a statement. The effect refers to a tissue that thickens when pulled on. Empa demonstrated the auxetic properties of nanofiber membranes developed specifically for this purpose and published the study in "Nature Communications". Among the range of applications for such materials is the ability to regenerate human tissue after injuries.

Researchers at Empa’s St.Gallen-based Biomimetic Membranes and Textiles lab developed matrix systems with auxetic properties that act as a structure for cells to grow and generate healthy replacement tissue following a complex injury. "If biopolymers such as polylactic acids are used in the spinning process, the membranes can even be degraded by the body," explained Empa researcher Giuseppino Fortunato.

The auxetic properties are important for the pore size of the membrane, because a tissue cell that is to colonize the “scaffold” has thus far been too large to fit snugly into the pore, writes the statement. The material developed in St.Gallen, however, stretches when pulled on without becoming thinner: volume increased about five-fold by volume and even 10-fold by thickness. "An auxetic effect of this magnitude is almost a world record," said Alexander Ehret of Empa's Experimental Continuum Mechanics lab. 

The concept is already patent pending. As well as applications in biomedicine, it can be used “for the treatment of wounds and tissue damage in locations as diverse as on the skin, in blood vessels and in internal organs or even in bone injuries”. It can also be applied in numerous other areas. “Membranes that can be activated by stress to release enclosed particles, adjustable filters or filling material that only expands to its final volume at the point of use are potential future applications,” write the researchers.