  Open source hardware has the potential to revolutionise the way we build
scientific instruments; with the advent of readily-available 3D printers,
mechanical designs can now be shared, improved and replicated faster and more
easily than ever before. However, printed parts are typically plastic and often
perform poorly compared to traditionally machined mechanisms. We have overcome
many of the limitations of 3D printed mechanisms by exploiting the compliance
of the plastic to produce a monolithic 3D printed flexure translation stage,
capable of sub-micron-scale motion over a range of $8\times8\times4\,$mm. This
requires minimal post-print clean-up, and can be automated with
readily-available stepper motors. The resulting plastic composite structure is
very stiff and exhibits remarkably low drift, moving less than $20\,\mu$m over
the course of a week, without temperature stabilisation. This enables us to
construct a miniature microscope with excellent mechanical stability, perfect
for timelapse measurements in situ in an incubator or fume hood. The ease of
manufacture lends itself to use in containment facilities where disposability
is advantageous, and to experiments requiring many microscopes in parallel.
High performance mechanisms based on printed flexures need not be limited to
microscopy, and we anticipate their use in other devices both within the
laboratory and beyond.
