Programmable Monomaterial for High-Tech Athletic Shoes

High-quality athletic shoes are usually made from a complex combination of materials. This has consequences for both production and recycling. In the ZiProMat project, Fraunhofer researchers have found another way. A sole made of programmable monomaterial performs various functions and is also made of the same material as the upper. The concept combines high-tech, sustainability and recyclability.

The sole fitted to high-quality athletic shoes has different properties in different zones. For example, the heel is especially well-cushioned to absorb the impact on the ground, the midsole is fairly soft to facilitate a smooth roll, and the tip is somewhat firmer. This necessitates the combination and joining of several different material properties.

Fraunhofer researchers have now developed a technology where the sole is made of a single material combining different functional zones. By designing the material structure with a specific configuration of ribs or ridges, Fraunhofer researchers can essentially program the behavior of the material under load.

In collaboration with sportswear manufacturer Puma, a team from the Fraunhofer Cluster of Excellence Programmable Materials CPM has already demonstrated the feasibility and benefits of this technology. The Fraunhofer CPM institutes have enlisted additional support in the ZiProMat follow-up project, which focuses on circular programmable materials.

The researchers are using a thermoplastic copolyester elastomer as the monomaterial basis for the sole. The soles are manufactured starting from she

ets of copolyester. These are heated and thermoformed using a vacuum to draw them into a mold that gives the sheet its predefined structure with ridges or ribs. The sheets are then stacked and joined together. This gives not only the outside of the sole but also the interior the special structure that is responsible for its mechanical properties.

The ultimate goal of the ZiProMat project is to establish a technology platform for the use of programmable materials and the development of pioneering recycling methods. The platform is intended to be applicable for various products and to incorporate all the materials used to the greatest possible extent in closed-loop recycling.

For more information, please visit the Fraunhofer website.