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Jaksa, et al.
A B C

Figure 7. Printing silicone rubber on top of PLA (A), then PLA on top of silicone rubber (B), and the resulting multi-material chips from
both tests (C) .
A B C

Figure 8. Silicone-PLA multi-material ribcage model based on a medical image of a newborn during printing (A), with support after
printing (B), and after support removal (C).
lack of internal support, but the external geometry stayed anatomic models in the future. The specifications stemming
intact. This bladder was also cut in half after printing to from this goal were printing multi-material structures
reveal the internal cavity (Figure 6C). out of at least one hard and one soft material, while also
The multi-material chips from the fourth (Figure 7C) being capable of printing empty cavities, infill structures
and fifth (Figure 7B) tests were also printable. Moreover, and thin-walled features. Considering the advantages and
in case of the fifth test, the PLA top was deformed, drawbacks of various AM methods and their applicable
presumably due to printing on a soft and unstable silicone materials, a printer was built that combines FFF and DIW
surface. After printing, the adhesion between the silicone technologies to print with a single-component silicone
and the PLA in the multi-material chips was evaluated rubber and a thermoplastic PLA filament.
by trying to manually separate the materials. The silicone The printing trials demonstrated that the established
was considered adhesive enough to resist this manual technology is capable of printing objects of both
peeling, since the bulk silicone material was damaged materials and can print silicone with a weakened internal
before the interface. structure (down-tuning) or combine silicone with PLA
After seeing the success of the five previous (up-tuning). An unsupported internal cavity and a thin-
tests, the ribcage model of the sixth test was printed to walled structure were also printable with the silicone. It
demonstrate the applicability of the printer to produce was shown that the FFF printhead can create hard support
medical image-based anatomic models (Figure 8). No structures. The strong adhesion between the PLA and the
complications were experienced during the printing silicone that was experienced during the tests suggests
process, although the manual removal of the support that this material combination can be applied to create
structures was challenging due to the adhesion between more complex multi-material structures, and that the
the silicone and the PLA. silicone must be cut away from the PLA in case of using
PLA for printing support structures under the silicone.
4. Discussion These assumptions were confirmed through the last test,
4.1. Overview of aims and results where the ribcage was indeed printable with PLA support
and sufficient adhesion between the silicone and the PLA.
The aim of this study was to build and test a 3D printer that These promising outcomes imply that the technology
enables features necessary for producing more realistic could be used to approximate the mechanical properties

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