Chitin Nanofiber Silk Self Assembled Biomimetic Composites
Abstract
In biological systems, the majority of structural materials and architectures (e.g. bone, teeth, wood, arthropod cuticles, crustacean exoskeletons, and mollusk shells) are composites that are formed from a dispersed phase, typically biomacromolecules hierarchically assembled into a fibrous form, and a matrix. For example, in arthropods, crustaceans, and mollusks, there is a dispersed phase of chitin nanofibers within a matrix of silk-like proteins. In wood, the dispersed phase is mainly cellulose, whereas in bone and teeth the dispersed phase is collagen. Biocomposites also serve as templates for mineralization to yield the final material. For example, the teeth of the mollusk chiton have magnetite mineralized on a template of chitin nanofibers, and the club of the Stomatopod Dactyl shrimp is composed of chitin nanofibers mineralized with hydroxyapatite. Rigid biological systems have frequently served as inspiration for biomimetic synthetic composites. One of the challenges in creating biomimetic composites, though, is recreating the complex hierarchical structure that is responsible for the outstanding properties of the composite. The hierarchical structure spans from the nanoscale to the microscale and that has been difficult to produce in large scale with top-down fabrication methods. In contrast, the self-assembly of biomolecular components with tailored molecules has proven useful. Biomineralized self-assembled composites have even been demonstrated. An appealing strategy for creating biomimetic composites is to exploit the self-assembly of ready to use natural components that do not require synthesis in vitro. In this regard, the Principal Investigator has recently discovered that a solution of chitin and silk in hexafluoroisopropranal self assembles into a biocomposite of 3 nm alpha-chitin nanofibers embedded in a silk matrix. This is the first self-assembled composite of its kind that closely mimics natural composites. The Principal Investigator has also explored crosslinking chitosan, a deacetylated form of chitin, with L-dopa before integrating it with silk, in order to mimic the chitin beak of squid, in which the density of cross-linked histidine residues in the proteins in squid beaks has been shown to dictate stiffness. In the proposed research, the PI will investigate the structure-processing-properties relationship of L-Dopa cross-linked chitin-silk based composites. Specifically, he will investigate the microstructure of the chitin-silk composites as a function of cross-linking. He will also characterize the mechanical properties (tensile, hardness) of the chitin-silk cross-linked composites as a function of cross-linking. The outcomes of these fundamental studies will be a series of phase diagrams where the chitin-silk cross-linking conditions can be more systematically related to materials on a time-dependent basis. These will form the basis for future devices and functions generated from these approaches. NOTE: This research project started under ONR Award N000141410724 to The University of Washington on 13-June-2014. It was planned to be a three year effort. In late 2015, the Principal Investigator assumed a position at The University of California, Santa Cruz. Therefore, a new award is being recommended to start at the University of California, Santa Cruz, to allow the PI to conduct a portion of the project there. The PI has left trainees behind at The University of Washington, so ONR Award N000141410724 will run to its original completion there, but with a reduction of $25,412 funds from the original total award value.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 23, 2016
- Source ID
- N000141612549
Entities
People
- Marco Rolandi
Organizations
- Office of Naval Research
- United States Navy
- University of California, Santa Cruz