From workshop to innovation

A workshop on programmable materials marked the starting point for a trailblazing development. “IF / THEN – Artificial Natures,” organized by the Fraunhofer Cluster of Excellence Programmable Materials (CPM), gave industrial designer Franziska Hagenauer the opportunity to explore these forward-looking materials in depth. An innovative collaboration project emerged from this creative exploration.

A fundamental issue in orthotics: despite elaborate custom fabrication, the precision of stabilizing medical devices such as orthoses is inherently limited — achieving a one-hundred-percent exact fit is hardly feasible in practice. On top of that, our bodies are constantly changing, especially during the healing process. Static orthoses can then become problematic and even cause further complications such as wound issues — particularly critical for patients with diabetes. The time- and cost-intensive manufacturing process compounds this problem, since every necessary adjustment requires a laborious remake.

This realization led to a pivotal question: what if a mass-produced orthosis could be individually readjusted to the wearer again and again?

From idea to prototype

The initial vision of an adaptive orthosis was based on a 3D-printed lattice structure with a wax coating. The key feature: when heated, the wax softens, allowing the structure to be reshaped. Where the material is compressed more strongly it becomes stiffer after cooling; where it is compressed less it remains more flexible. This allows both the shape and the stiffness of the orthosis to be customized — comparable to a wax seal that is heated, formed, and then solidifies again. The same property also enables more efficient production of the orthosis in a flat form and in standard sizes.

This concept was presented in the final project exhibition together with the other workshop results at Galerie HINTEN in Chemnitz. The idea met with such positive feedback that it was selected for further development in cooperation with the Fraunhofer Institute for Machine Tools and Forming Technology (IWU) in Dresden. This is where the WEAM technology (Wire Encapsulation Additive Manufacturing) developed at Fraunhofer IWU came into play. This innovative 3D printing process integrates heating wires directly into the polymer during printing — similar to a filling in a sandwich. When these wires are electrically heated, the surrounding plastic becomes moldable like putty and then solidifies again in its new shape after cooling.

The perfect balance between comfort and stability

Working with an orthosis manufacturer, the team developed an optimal layer system for the orthosis core. Two layers form the heart of the structure: a body-facing, flexible layer provides comfort, while an outer layer ensures the necessary stability.

For the body-facing layer, the team first experimented with thermoplastic polyurethane (TPU) structured as a gyroid — a so-called “triply periodic minimal surface” that also appears in nature, for example in butterfly wings. This evolutionarily optimized structure distributes loads evenly and offers excellent shock absorption.

The stabilizing outer layer was made from thermoplastic polylactide (PLA). In combination with the integrated heating wires, this yields ideal properties for orthoses. The resulting material composite could be electrically heated and hand-formed to a model foot — creating the perfect orthosis core.

Further development for practical use

As part of the “Artist/Designer in Lab 2023” funding program of the Fraunhofer Network for Science, Art and Design, the team refined the concept further. After several design iterations, they chose neoprene as the soft, body-facing layer onto which the hard layer can be printed directly — a combination particularly suitable for orthoses worn inside a shoe.

The finished prototype features user-friendly snap fasteners for contacting the heating wires, protective caps, and a clever attachment system with a heel-mounted hook-and-loop strap and a quick-lacing system at the front.

A bridge with many advantages

The benefits of this innovative orthosis are compelling: an ergonomically perfect fit that can be readjusted at any time — and can even be reused for other patients with the same shoe size. Adjustment time at the orthotist’s can be reduced by 50 to 75 percent, while production time — thanks to planar 3D printing — is only about one tenth of conventional 3D-printed orthoses.

The prototype, presented among other venues at Formnext 2024 in Frankfurt, illustrates the potential of programmable materials in combination with modern manufacturing techniques. Products can be produced in series — cost-efficiently and quickly available — and then tailored precisely to patients. Improved wearing comfort supports the healing process, while lower material consumption and shorter manufacturing steps conserve resources.

Programmable materials thus prove to be effective bridge-builders between the seemingly contradictory requirements of mass production and individual customization — a development whose potential extends far beyond orthotics to numerous application areas.