Image: Three-dimensional printing can manufacture precise insoles for diabetic patients (Photo courtesy of UMSICHT).
A new technique to digitalize the mechanical properties of insoles and use three-dimensional (3D) printing to manufacture them could help avoid diabetic foot ulcers.
Developed by researchers at the Fraunhofer Institute for Mechanics of Materials (IWM; Freiburg, Germany) and the Fraunhofer Institute for Environmental, Safety, and Energy Technology (UMSICHT; Oberhausen, Germany), laser-assisted construction of customized footwear (LAUF) is based on the physical properties of thermoplastic polyurethane (TPU). The optimization of the 3D structure and shape of TPU, when used for insoles, determines how soft or rigid the insoles are.
3D foot mapping data is processed using application-oriented load simulations to resolve which structures are needed, and where to achieve the desired properties in the insole. The data is then sent to the 3D printer, where the insoles are printed using selective additive laser sintering. Once an insole has been printed, it is returned the IWM, where it is tested to the point of failure using tensile, abrasion, and bending tests. The first prototypes have already been produced in this way, and the researchers predict that within a few years, insoles can be produced at greatly reduced cost.
“Digital foot mapping is already common practice. As part of this project, we have now also completely digitalized the insole production process. Using newly developed software, the orthopedic shoemaker can design an insole for an individual patient and can print out the result on a 3D printer,” said Tobias Ziegler, PhD, of the IWM. “Where does an insole need to be soft, or more rigid? By altering the structure type, we can precisely determine the rigidity of the insole.”
Diabetes patients often suffer from nerve and circulation problems in the feet, which reduce their perception of pain. The nerve pathways that ensure that weight is automatically transferred from one foot to the other during prolonged standing are disrupted, and as a result, diabetics do not notice that their toes, heels, or the balls of their feet are too heavily loaded. The foot receives no relief, and pressure sores, ulcers, and infections may go unnoticed. Serious cases may even lead to amputation.
Fraunhofer Institute for Mechanics of Materials
Fraunhofer Institute for Environmental, Safety, and Energy Technology