DIATOMS FOR NANOMANUFACTURING - New Principles for Orientation and Immobilization

Abstract: Diatoms, unicellular micro-algae are one of the most common types of phytoplankton encased inunique cell walls made of silica (hydrated silicon dioxide) called frustules.' The cell wall is composed ofbiogenic silica extruded by the cell which is synthesized intracellular by polymerization of silicic acidmonomers. Individual cells could manufacture highly accurate 3D structures in silica from nano meterto micro meter range. Diatoms create scores of very complex three-dimensional structures on a scalewhich would otherwise be content to create two-dimensional structures. The silica shell could beused as a template to produce a replica in other materials.In the Vinnova project “Genome based Manufacturing” we investigate how diatoms could be utilizedto produce 3D micro-and nano-structures. Different methods to orient and immobilize the diatomsare investigated by us at Swerea IVF. Asymmetrical benthic diatoms such as “Surirella Sp” are used forthe project. A marine biologist, Anna Godhe at Department of Marine Ecology, University ofGothenburg and a researcher, Anders Blomberg at Department of General and Marine Microbiology,University of Gothenburg are working with the characterization and principles to manipulate thegenome of diatoms and to control the structure built by the algae, which is another part of theVinnova project.Microstructure for orientation and immobilization of Diatoms:For the orientation and immobilization of the diatoms we designed a PDMS stamp forprinting of organic and inorganic materials on glass substrate and a patterned glass plate forlight illumination. The diatoms are attracted to light and the working hypothesis is that theywill creep towards the light and reside on the illuminated spot.Motile diatoms move for a while and then slightly adhere to the surface. By understandingthe chemotactic, phototactic and adhesion behaviors, we can get the diatoms to move intospecified positions, say on a micro-patterned substrate, and then once they are in placeconvert them into organized arrays of nanotechnology components.Diatoms have the ability to make their movements directive and useful for them in the slightest way.Photosynthetic in nature, light is the primary energy resource, therefore, orientation and movementcan be controlled by light-based mechanisms. Here we use patterns having 20 μm size spots at adistance of 200 μm to observe the motility of diatoms regulated by light source or nutrient. The aim isthat the diatoms move to the patterned area, and when they are oriented according to the pattern,we immobilize them. As a result, 3D array of silicon is obtained which could be used formanufacturing of complex micro /nano-structures. In the microelectronics industry fabrication basedon conventional 2-D layer-by-layer techniques can be replaced, and low-cost mass production ofnanostructured devices with intricate 3-D shapes is possible.