3D printed artificial body parts
VirtaMed is a Swiss company that develops and produces highly realistic medical simulators for training and education. Their systems consist of two main parts, a virtual reality envoirenment and a (matching) physical reproduction of a realistic anatomical model. The challenge is to realistically reproduce the different mechanical properties of the tissues, which merge seamlessly into one another in the body.
The (existing) manufacturing process for these components is very complex and includes (multiple) casting processes with several materials, in which other components are alsoembedded/enclosed. This process has been tried and tested in series production as well as for prototypes and is usually carried out abroad. However, it slows down the innovation and development process enormously.
To accelerate innovation and development, the applicability of 3D printing, so-called Additive Manufacturing (AM), was investigated. In this field, Multi Material Jetting technology (MMJ) is the only one that can be used to simulate the hard and flexible areas in several gradations in one component.
The additive manufacturing technology will be used to create prototypes for later series production. As a first step, some test models were produced to examine the integrity and thus the stability of the contact surfaces between the different materials. For this purpose, flexible cubes with cylinders of hard material attached to them were printed. The test models were handed over to VirtaMed for testing.
Using the experience gained from the test models, a flexible ligament was printed using MMJ technology. Specifically, the Coracoacromial ligament, a band that serves to stabilise the shoulder joint. It is firmly attached to the hard bone at both ends, is flexible in the middle and has a continuous transition from flexible to hard in the areas between.
The feedback from VirtaMed on this component, which was actually only intended as a prototype for development, was so positive that the question of its possible use as a component in the final product arose. The consideration of using this manufacturing process for production and not only for development led to the question of whether the materials had sufficient load capacity and durability for use in the simulator.
In order to investigate this question, it was decided to carry out some fatigue strength tests with the above mentioned component.
It turned out that a detachment or separation at the material interfaces would not be a problem. Investigations showed that the components cracked in the plane of the smallest cross-sectional area and not along a material interface. Thus, the test model achieved only 10 % of the required load cycles in the fatigue strength test.
In conclusion, it can be said that the MMJ has proven itself for the production of prototype parts and can lead to a higher agility of VirtaMed in product development.
In order to finally clarify the usability of AM components in the final product, further fatigue strength tests would be necessary which correspond to the normal use of the simulator. Further materials would also have to be developed to ensure that the components have a sufficient service life.
With the knowledge gained from the prototypes, there is the possibility of additionally expanding the spectrum of possible components. As during this project new component generations for MMJ have already been developed, which now also make it possible to produce even softer components. With these experiences one could consider for example gynaecological and visceral simulators.
