  Droplet-based microfluidic systems are a promising platform forlab-on-a-chip
(LoC) applications. These systems can also be used toenhance LoC applications
with integrated droplet control information or for data transmission scenarios
in the context of molecular communication. For both use-cases the detection and
characterisation of droplets in small microfluidic channels is crucial. So far,
only complex lab setups with restricted capabilities have been presented as
detection devices. We present a new low-cost and portable droplet detector. The
device is used to confidently distinguish between individual droplets in a
droplet-based microfluidic system. Using on-off keying a 16-bit sequence is
successfully transmittedfor the first time with such a setup. Furthermore, the
devices capabilities to characterise droplets regarding colour and size are
demonstrated. Such an application of a spectral sensor in a microfluidic system
presents new possibilities, such as colour-coded data transmission or analysis
of droplet content.
