Self-Monitoring Plastics? Glasgow Researchers 3D Print Auxetic Materials

Picture yourself stretching a material, say, a rubber band. The more you stretch it, the thinner it becomes. A group of researchers from the University of Glasgow designed a material that does the opposite: plastics that grow wider when pulled. These are classified as auxetic materials, and the researchers achieved this unique behaviour by carefully engineering and 3D printing internal geometries. But how exactly are these plastics made, and what are their applications?

Late this June, the team reported a breakthrough in developing and designing novel auxetic structures using high-performance engineering plastics. The research, published in Materials Horizons, demonstrates how additive manufacturing can create self-monitoring materials with programmable properties like strength, stretchability and strain sensitivity. In general, auxetic materials have extraordinary mechanical characteristics, like enhanced energy absorption and improved damage tolerance, so the plastics developed by the Glasgow team have potential for many applications.

Illustration of the Glasgow study (Photo Credit: Johannes Schneider et al./Materials Horizons)

The researchers used an FDM Apium P220 3D printer from Apium Additive Technologies GmbH, with PEEK, to create these structures. PEEK is a strong, semi-crystalline thermoplastic that is not only heat and wear resistant but also capable of substituting some metals due to its strength-to-weight ratio. Furthermore, the material is lightweight and biocompatible, already widely used for engineering and biomedical purposes. Using PEEK allowed the researchers to precisely control both mechanical and electrical behaviour.