Feature article: PIM International, Vol.4 No. 2 June 2010, pages 49-52, 2125 words

Authors: Janne Haack Dipl.-Ing. (FH), Dr. Philipp Imgrund, Dr. Sebastian Hein, Vera Friederici, Dr. Natalie Salk, Fraunhofer-IFAM, Germany

Biomaterials Technology, Fraunhofer-IFAM, Wiener Straße 12, 28359 Bremen, Germany

Powder Injection Moulding is an established process for the manufacture of medical products from biocompatible materials. Processing innovations have, however, enabled a wider range of functional products to be considered than ever before.

Philipp Imgrund and colleagues from IFAM, Bremen, Germany, present current work that includes degradable PIM implants, surface structured PIM products for implant applications, and implants with controlled porosity. The challenges of series production are also addressed.

Introduction 

The variety of materials and complexity of components makes powder injection moulding (PIM) attractive for the production of medical products and implants.

For commercial processing of biocompatible materials (e.g. metals: 316L stainless steel, Co-Cr-based alloys, titanium alloys; or ceramics: alumina, zirconia) metal injection moulding (MIM) and ceramic injection moulding (CIM) are already successfully established.

In recent years the scope of powder injection moulding technology has expanded from standard powder based materials to a considerable range of functional materials and composites for medical use. Besides mechanical stability, they need to provide specific medical features such as bioactivity, degradability, or porosity and surface structure.

This article presents current developments in the processing of biodegradable composites, the powder injection moulding of implant materials and the production of implants with defined surface structures while keeping tight processing tolerances.  

Further sections of this feature include:

- Biodegradable composites

- Injection moulding of PLA, HA and metal implants

- Bioactive surfaces by Micro MIM

- Towards production of micro implants

- Conclusion

Figures and Tables:

Fig. 1 PLA / HA composites with different porosity

Fig. 2 Interference screws made by injection moulding of PLA (left), hydroxyl apatite (centre), and 316L stainless steel (right)

Fig. 3 a) Image of a sample with a hemispheric surface micro pattern; b) SEM documentation of surface with 50 µm hemispheres

Fig. 4 Hemispheres produced via µ-MIM with a diameter of 5 µm and interspacing of 20 µm Fig. 5 SEM documentation of an osteoblast cell seeded on the surface patterned by µ-MIM

Fig. 6 Injection moulded stapes made of stainless steel

Fig. 7 Measurement positions for determining the tolerances of the titanium stapes

Fig. 8 Weight measurements of 90 titanium stapes

Table 1 Characteristics of the sintered titanium stapes at steady state conditions