Towards uniformly oriented diatom frustule monolayers: Experimental and theoretical analyses

• Published in: Microsystems & nanoengineering 2016-12, Vol.2 (1), p.16064-16064, Article 16064
• Main Authors: Li, Aobo, Zhang, Wenqiang, Ghaffarivardavagh, Reza, Wang, Xiaoning, Anderson, Stephan W., Zhang, Xin
• Format: Article
• Language: English
• Subjects: 639/301/357/537; 639/925/357/537; Engineering
• ISSN: 2055-7434; 2096-1030; 2055-7434
• DOI: 10.1038/micronano.2016.64

Diatoms are unicellular, photosynthetic algae that are ubiquitous in aquatic environments. Their unique, three-dimensional (3D) structured silica exoskeletons, also known as frustules, have drawn attention from a variety of research fields due to their extraordinary mechanical properties, enormous surface area, and unique optical properties. Despite their promising use in a range of applications, without methods to uniformly control the frustules’ alignment/orientation, their full potential in technology development cannot be realized. In this paper, we realized and subsequently modeled a simple bubbling method for achieving large-area, uniformly oriented Coscinodiscus species diatom frustules. With the aid of bubble-induced agitations, close-packed frustule monolayers were achieved on the water–air interface with up to nearly 90% of frustules achieving uniform orientation. The interactions between bubble-induced agitations were modeled and analyzed, demonstrating frustule submersion and an adjustment of the orientation during the subsequent rise towards the water’s surface to be fundamental to the experimentally observed uniformity. The method described in this study holds great potential for frustules’ engineering applications in a variety of technologies, from sensors to energy-harvesting devices. Microstructures: Scalable production of uniform diatom monolayers A simple technique for harnessing the remarkable properties of algal exoskeletons could lead to advances in nanotechnologies. Frustules, the silica cell walls of diatomic algae, are intricate and multilayered porous structures with extraordinary strength, large surface areas and unique optical characteristics. Controlling the alignment and orientation of the frustules is key to exploiting their attributes but has so far proved challenging, limiting their potential applications. Now, Xin Zhang at Boston University in Massachusetts, United States, and her colleagues have developed an efficient method for generating uniformly oriented frustules. The team pumped nitrogen bubbles under water, on which the dish-shaped frustules floated, forming clusters of closely packed, similarly oriented frustule monolayers on the surface. Their findings demonstrate a scalable process for producing large areas of aligned frustules that could facilitate micro/nanomanufacturing of biotemplated structures for a host of practical technological applications.