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

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 12.6 ± 4.0 µm in length and 75 ± 21 nm in diameter (outer fultoportulae) or 17.5 ± 4.7 µm in length and 170 ± 39 nm in diameter (central fultoportulae), yielding high aspect ratios of ~168 and ~103 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 pure biogenic β-chitin microrods.