LAuF: Tailor-made insoles for diabetes patients

Laser-assisted construction of customized footwear

© Fraunhofer IWM /Felizitas Gemetz

Customized insole

By combining different structures in an insole, its local stiffness can be digitally adjusted.

© Fraunhofer IWM /Felizitas Gemetz

3D structure

3D structures made from TPU for insoles. The structures were designed using CAD, their properties simulated, and compared with experiments.

Project aims

The aim of the joint project LAuF was to fully digitize the production of insoles for diabetes patients: from measuring the foot to the manufacturing process for the insoles using additive manufacturing. The aim is to optimize the insoles and make their production more cost-effective.

Benefits

Insoles can provide targeted relief for the feet of diabetics in already damaged areas. For this purpose, the shape and, in particular, the local hardness (stiffness) of the soles must be adapted to suit the patient's foot. With the method developed in the LAuF joint project, orthopedic shoe technicians can design such insoles individually for each patient on the computer and produce the result with a 3D printer. By combining different three-dimensional structures in the sole, their local stiffness can be digitally adjusted. Compared to handmade production, the sole can thus be adjusted much more finely to the patient's foot. In addition, the digitalized process enables the product to be evaluated scientifically: Since the data was previously recorded digitally, the mechanical properties of the insoles, for example, can be better analyzed. This enables the orthopedic effects of the insoles to be assessed on a patient-specific basis and, if necessary, the soles can be optimized in a more targeted manner.

Result

The LAuF joint project has succeeded in completely digitizing the production process for insoles for diabetes patients: from measuring the foot to manufacturing and subsequently evaluating the orthopedic product. In order to adapt the flexibility of the sole very precisely to the requirements of the foot, special spring elements with a very fine resolution (5x5 mm2) are integrated into an intermediate layer of the sole. Each of these spring elements can have a different stiffness locally in the sole. Selective laser sintering (SLS) is used to manufacture the insoles as one component. Such delicate structures can be created effectively with the additive production process. The material used to produce the insoles is thermoplastic polyurethane (TPU), which is ideally suited to the high demands in the sole. TPUs with different Shore hardnesses were tested in the project.

Project partners

  • Fraunhofer-Institut für Werkstoffmechanik (IWM)
  • IETEC Orthopädische Einlagen GmbH Produktions KG
  • Sintermask GmbH
  • Lehmann & Voss & Co. KG
  • rpm rapid product manufacturing GmbH
  • Explius GmbH
  • Covestro

Funding
Duration: May 2015 to April 2018
Funding code: 03XP0010A-F
Website: www.bmbf.de