One of my colleagues is studying diatoms in lakes in Antarctica. However, normally sampling diatoms involves getting wet, which is not terribly fun in Antarctic conditions. To get around this, we developed this sampler, allowing users to scrub and siphon diatoms from almost 1m below the surface, without coming in contact with the water.

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In terms of hardware, it’s quite cheap to make, requiring a handful of m3x20mm bolts, and 2 m5 x 75mm bolts. Stainless steel hardware is recommended. The poles are extruded aluminium poles of 16 and 25mm external diameter and 1m in length. It uses standard 50ml syringes with a centred nozzle.

This is just the first prototype, and there is a big list of improvements to be incorporated into future versions. In particular:
• Overall size to be decreased – to make it easy to transport. Currently the outer diameter is ~125mm, which makes it difficult to make a protective tube for transport. Ideally I’d like to get the diameter down to ~90mm, so it can fit into a PVC tube. This change will also cut down on plastic required.
• Syringe inlet to have improved access for cleaning and to make sure it is free of obstructions.
• Toothbrush clamps to be more adaptable. Current design limits the width of the toothbrush and doesn’t fit very angled toothbrushes very well.
• Use a rubber seal with a mechanical attachment, rather than glued foam.
• An outlet so that the sample doesn’t flow back out through the base of the shield in a haphazard fashion when the syringe is depressed.
• An tool free way to replace the syringe.

To build:
• Print all the components, (print 2 of the pole clamps and of each toothbrush clamp).
• Trim around 80mm from the 25mm aluminium pole. You’ll need to fine tune this measurement if you want the scrubber handle locking pin to lock into place.
• Clamp the outer shield and pole clamps and slide the gasket onto the 25mm pole.
• Clamp the scrubber onto the 16mm pole
• Clamp they syringe clamp onto the other 16mm pole
• Attach the other syringe clamp to the outer shield with the m5 bolts.
• Slide the poles together, and clamp the scrubber handle to the top of the scrubber, and the syringe handle to the top of the syringe pole. You may need to fine tune the handle position if you want the locking pin to fit.
• Bolt the toothbrush clamps with the open ends outwards. Slide some toothbrushes in and tighten the clamps.
• Glue some foam to the base of the shield so that it can seal against the rock.
Note: Some sanding may be required as some of the components are quite tight tolerances.

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To use:
• Release the locking pin on the scrubber handle.
• Stick the sampler up against an underwater rock.
• Push the scrubber handle down until the toothbrushes contact the rock.
• Scrub, scrub, scrub.
• Pull up the handle and engage the locking pin.
• Pull up the syringe handle to capture your sample.

You can find this design, and a bunch of other things I’ve designed at my thingiverse page.

What’s next on my list of things to blog about? I have a bunch of things on my table. Hopefully my next post will occur in less than a year. 😀

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