Ro(a)d to New Functional Materials: Sustainable Isolation of High Aspect Ratio β-Chitin Microrods from Marine Algae

Chitin, as the most abundant polysaccharide in the marine environment, is of prominent interest in the light of sustainable development and sea waste usage. High aspect ratio rod-shaped chitins such as chitin whiskers, or chitin nano- and microfibers are particularly promising for a wide range of applications, including electrorheological suspensions, lightweight reinforcement material for biocomposites, biomedical scaffolds and food packaging. Here, we report the first mild water-based mechanical extraction protocol to isolate β-chitin microrods from the marine algal species Thalassiosira rotula while preserving their structural integrity throughout the process. The resulting microrods could be distributed into two populations based on the fultoportulae from which they are extruded. The rods exhibit typical dimensions of 14.3 ± 4.8 µm in length and 75 ± 21 nm (outer fultoportulae) or 170 ± 39 nm (central fultoportulae) in diameter yielding high aspect ratios of ~191 and ~84 on average, respectively. Due to this environmentally friendly extraction, the high purity of the synthesized chitin, and the renewable algal source, this work introduces a sustainable route to produce relatively pure biogenic β-chitin microrods.