Figure 18a shows that 3D printed light pipes currently suffer
from increasing light loss with distance. Adding curvature to
a light pipe further increases light loss when compared to a
straight light pipe of equal length (Figure 18b). We believe
this limited performance is due to two factors. Firstly, the
contours where two different materials intersect are currently
not perfectly smooth (Figure 19). Microscopic unevenness
on internal surfaces result in light being lost or redirected
in unpredictable ways. However, we found the consistency
between ten identical 50mm straight prints to be high, with
a standard deviation of 0.0822V when measuring transmittance
as previously described. Secondly, although we know
the refractive index of the core material, no information is
available for the refractive index of the cladding material.
Because we use support material that is not intended as an
optical material, its performance as cladding is understandably
low. We can assume that the refractive index of each
material is close enough to restrict the angle of incidence to
a relatively small value and thereby limit internal reflection.