Designing a 3D-printed flow chamber

I’m working on a small, water-tight chamber to measure how flow affects feeding kinematics in Vorticella, a single-celled protist that adheres to surfaces.

There are some real design constraints, namely that it must be small enough to accommodate the relatively short (10mm) working distance of the objective lens we’re using.

I designed a prototype in Solidworks. The clear interrogation area in the center is a 10mm cuvette with the bottom cut off. There’s an additional 1/16″ gap at the bottom to accommodate a slide which will hold the Vorticella.

Then I used COMSOL and to model the velocity profile to ensure we’d get a nice parabolic flow. If you haven’t used SimScale, I highly recommend it. It will even do multiphysics, including FEA and thermodynamics. SimScale represents the future of physical modeling–it has a simple setup and utilizes cloud infrastructure for excellent processing speeds.

This took a bit of work–COMSOL makes you pay for a CAD Import Module (which we don’t have) and so running this simulation required remaking it in their software. Totally lame. SimScale, by comparison was a breeze. The results were, as expected, the same across both platforms.

The working area of the chamber has a nice parabolic velocity profile, and the Vorticella should be clear of any potential eddies. At this scale (Re << 1), flow is laminar so we can ignore turbulence.

I made a few modifications to allow the objective to fit and had the UPS Makerspace print it. Here’s the almost-finished product:

It’s held together with 4 pieces of 2mm stainless all-thread and a 4mm nuts.

I still have to drill and tap the inlet/outlet connectors. I’ll update once complete.

You can download the Solidworks parts here:

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