Diatom Actinoptychus

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Actinoptychus senarius is a relatively large (between 150-20µm), strongly sculpted and heavily silicified diatom. It is widely distributed throughout the world's oceans and commonly found in the North Sea, where its unique characteristics have been extensively studied. The frustule geometry of this remarkable organism is characterized by a prominent central area and six areolated sectors with alternating raised and depressed areas. Diatoms like Actinoptychus senarius are unicellular algae that contribute significantly to global primary production, making them essential components of the marine ecosystem. Their success has been largely attributed to their silicified, intricate lightweight shells, which provide efficient protection against grazers and other predators. The distinctive "pillbox design" of these diatoms consists of two overlapping halves, allowing repeated cell division to lead to a considerable reduction in overall cell diameter within a diatom culture. For detailed analysis, researchers have employed advanced 3D imaging techniques. Diatoms were labelled with the fluorescent dye PDMPO and placed in a medium for observation. Using a fluorescence microscope, newly synthesized valves were easily distinguishable, and 3D images were reconstructed from confocal laser scanning microscope images. These intricate models were created using specialized software such as rhino/grasshopper and blender. To create accurate physical replicas of these diatoms, researchers have utilized 3D printing technology. A large model with a diameter of 700 mm was printed in PLA using an FDM printer with a Ø 1.2 mm nozzle and 0.4 mm layer height. This process consumed around 12 kg of material, with approximately 40% consisting of removable support structures. However, the two shells designed to fit together exhibited a tight fit due to warping and inferior surface quality. To resolve this issue, researchers manually postprocessed the inner shell, which sometimes requires scaling down the design for optimal results. A smaller model printed on a powder bed printer with a diameter of Ø 150 mm proved successful, with both parts fitting together seamlessly. For added functionality, the model features a Ø 41 mm bore at the bottom, allowing it to be placed on a corresponding pole as a showcase. This remarkable replica serves as a testament to the intricate beauty and complexity of diatoms like Actinoptychus senarius. The creation of these models has been a collaborative effort between researchers from various institutions. The team responsible for this project includes Sonja, Corinna, Lars, Marvin, and Leonard, who worked together to cultivate the diatoms, prepare them for 3D imaging, and refine the design for 3D printing. Their work can be found on the AWI's website at https://www.awi.de/en/science/special-groups/bionics.html. For further information or questions, please do not hesitate to contact the researchers directly.