Diatom Actinoptychus

Actinoptychus senarius is a relatively large (between 150-20µm), strongly sculpted and heavily silicified diatom. It is widely distributed throughout the world oceans and commonly found in the North Sea. The frustule geometry is characterised by a prominent central, massive area and 6 areolated sectors with alternating raised and depressed areas. Diatoms are unicellular algae, which contribute significantly to global primary production. Their success has been largely attributed to their silicified, intricate lightweight shells, which provide efficient protection against grazers. Due to their peculiar “pillbox design”, which consists of two overlapping halves, repeated cell division leads to a considerable reduction in overall cell diameter within a diatom culture.

For 3D-analysis, the diatoms were labelled in a medium containing the fluorescent dye PDMPO. Newly synthesized valves were easily distinguishable in a fluorescence microscope and 3D images were reconstructed from images taken by a confocal laser scanning microscope. The 3D-Model was completed as a full valve using rhino/grasshopper and blender.

The 700 mm model was FDM printed in PLA with a Ø 1.2 mm nozzle and 0.4 mm layer height – one half took 14 days straight and consumed around 12 kg of material of which 40 % were removable support structures. The two shells were designed to fit into each other with a gab of 2 mm in between and a draught of 3° (Ø 700 mm diatom). Nonetheless the fit was too tight due to a bit of warping and inferior surface quality. The inner shell had to be postprocessed manually. Depending on the quality of your printer you might have to scale down the inner shell slightly to achieve an appropriate fit. A Ø 150 mm model printed on a powder bed printer came out fine and both parts joined nicely.

Since the model is used as a showcase it has a Ø 41 mm bore at the bottom so it can be placed on a corresponding pole.

Credits: Sonja /Corinna / Cultivation, Lars CLSM/ Dying, 3d-images, Marvin/ Leonard: Model finish for 3D-Printing. So far, models between 50 and 700 mm have been printed.

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