This is a cuvette with a 500 um internal microfluidic channel.
The channel is comprised two sections, a straight channel down the side and a snaking path through the middle. This to fill the fluidic to works best to inject your liquid in the the straight channel and have it flow up the snaking one.
Optimum print conditions (using an Ultimaker 2) were 0.1 mm layer height and 50 mm/s extrusion speed. It looks best if you use one of the transparent plastics otherwise you won't see the internals.
We have had some duchess passing low concentration (5%) acetone in IPA through the channel to smooth out the internal features. But it will work fine without
This was original designed by my student Alex Tothill.