This article was written by Andrew Rankin of Sovrin
Plastics and Peter Manser of Battenfeld Uk. This is Page
3 of 3.
Applications
As the micro moulding technique has evolved, a
number of new materials and alloys have been developed, especially
polylactide/polyglycolide (PLGA). These include specialist liquid
crystal polymers and resorbable materials that are being formulated
as alloys for particular end-use performance. Inevitably, commercial
confidentiality limits the information being freely available. In
the future, surgical procedures will be simplified and patient trauma
reduced by using resorbable components in tissue repair. Developments
in the orthopedic field are also providing opportunities to enhance
repair and restoration techniques. These include some fine detail
components used for repairing and restructuring bones without the
need for subsequent removal of temporary supporting items.
The correction of severe hearing problems using
cochlear ear implants requires small and accurately formed components.
These are now being successfully produced after several years of
development (Figure 5). In the future, the so-called lab-on-a-chip
technology, where exploration of blood vessels and controlled local
drug delivery, will be possible using micromodules, presents an
exciting and challenging development. The individual components,
comprising vision and detection components that provide the basic
structures of these devices, are fabricated using micromoulding
techniques.
Figure
5: |
Cochlear
ear implant in position |
|
Design proficiency
As well as the processing skills required for micromoulding,
design skills for components of this size also need to be developed.
Components with fine detail require careful original design with
a novel and sometimes unconventional approach that would not be
possible with conventional moulding. In particular, the increasing
choice in moulding materials requires a comprehensive appreciation
of the possibilities. Some innovative solutions including a combination
of two or more materials have been produced using micromoulding
technology; for example, a combination of moulding materials can
be used with only selected areas capable of metallic plating to
enable the creation of small connectors.
Mould manufacture
Many of the established conventions in mould manufacture
no longer apply when dimensional details are expressed in microns.
Specialised machining techniques have been developed that include
microelectrical discharge machining and high- speed milling with
small cutters on extremely stable polymer granite bed machines,
which enable some ultra-fine details to be produced in moulds for
injection moulding. Milling cutters as small as 0.1 mm in diameter
are now being used to machine to micron level. Techniques have also
been borrowed from the lithography industry and silicon wafer production
to create ultra-fine microstructure details.
