Rapid Form Copying and Rapid Mould-Making Systems for Biodevices - Advanced Design and Manufacturing Technologies for Biomedical Devices - page 203

Even though every year novel technologies appear and the use of more and
more polymeric, metallic, ceramic materials is possible (Wohlers 2010 ) and some
recent advances are even aiming at the manufacture of 3D biodevices by deposi-
tion of biological materials (Mironov et al. 2009 , see Chap. 14 ) , it is still true that
many of the widely available technologies providing the best quality (precision)/
cost relationship cannot directly work with materials adequate for in vitro, ex vivo
or in vivo trials.
For instance, as already detailed, many technologies working on the basis of
photopolymerisation processes (laser stereolithography, digital light processing,
polyjet, etc.) usually work more properly with materials such as epoxy or acrylic
resins, which are not adequate for fi nal biodevices, due to their toxicity. In other
cases, some technologies include a powder material (ceramic, polymeric, metallic
or even biological, including wood powder) and a second gluing material, as hap-
pens with conventional three-dimensional printing, what typically leads to non-
biocompatible parts, due to the toxic effects of the gluing agent.
The use of alternative materials to those provided by the machine manufacturers
can damage the prototyping machine and always goes at the researcher ' s own risk,

as machine s guarantee does not cover such kind of “personalisations”, being usu-

ally an expensive, although also a highly interesting, strategy.
Of course some companies are aiming at broadening their materials portfolio and
trying to include at least non-toxic materials for some research tasks linked to bio-
medical engineering. However, most relevant advances linked to the 3D structuring
of biomaterials are still carried out by researchers at universities; some examples are
included in the reference section (Stampfl et al. 2004 , 2008 ; Manjubala et al. 2005 ;
Infür et al. 2007 ; Schuster et al. 2007a , b ).
Therefore, rapid tooling still provides several highly remarkable alternatives, for
obtaining prototypes in more adequate materials for fi nal purpose, especially if the
use of biomaterials is required (as is usually the case in the development process of
novel biodevices, when the different in vitro, ex vivo and in vivo trials are required),
than most of the currently available rapid prototyping technologies.
In fact many biomaterials are diffi cult to be structured in an additive way but are
indeed very apt to other conformation processes, such as casting, injection mould-
ing stamping or hot embossing, and the use of rapid tools and rapid moulds proves
to be very adequate for the rapid manufacture of prototypes for trials, as the case
studies included in the following sections detail.

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11.3 Case Studies: Manufacture of Biodevices by Vacuum

Casting in Rapid-Copied Silicone Moulds

The process of silicone (also polydimethylsiloxane or “PDMS”) mould manufacture,
based on a master model obtained normally through rapid prototyping, involves
some steps described further on. We concentrate on the process aimed at obtaining
a two-part mould, as the process for obtaining a single cavity is simpler.