UC San Diego

Applications bioinspired by sea urchins and spongy bone are described herein. First, a bioinspired protocol is implemented for development of a bioinspired sediment sampler based on a progression through four broad categories that include biology, materials science, bioinspiration and bioexploration. First, the sea urchin mouthpiece, Aristotle’s lantern, and its open and close mechanism was observed for examination of the natural biological structure. Second, the Aristotle’s lantern and tooth microstructure were analyzed in further detail with several materials science characterization methods. Third, a sediment sampler bioinspired by the open and close mechanism of the Aristotle’s lantern was designed and fabricated through an iterative prototyping process. Fourth, engineering analysis methods were used to explain why a tooth reinforcing keel structure evolved in the biology of modern sea urchins. Our bioinspired protocol was therefore a circular rather than linear process. The biology initially guided the bioinspired design to a typical endpoint, however, further analysis of a specific aspect of the bioinspired tooth design helped justify how the biology evolved.

Magnetic field assisted ice templating, also known as magnetic freeze casting, was used to align surface magnetized ceramic particles in water into chains to make multi-axis strengthened porous scaffolds bioinspired by spongy bone. Magnetized particles aligned in the ice crystal growth direction and into chains that formed lamellar walls in the applied transverse magnetic field direction during the magnetic freeze casting process. Aligned lamellar walls in the axis transverse to the ice crystal growth direction stiffened the porous scaffold similarly to spongy bone with multi-axis aligned porosity. Magnetized particle chain alignment in the scaffold center during magnetic freeze casting depended on several factors, including magnetic field strength, magnetized particle moment, particle size, length of time before freezing, slurry temperature and slurry concentration. Magnetic freeze casting was done with different magnetized alumina particle sizes and morphologies followed by mechanical compression in different axes.

Magnetic freeze casting with a lower applied magnetic field for larger magnetized hydroxyapatite particles was implemented based on preliminary empirical findings and agreed with predictive equations based on theory. Radial strengthening by shrink wrapping scaffolds with a biodegradable polymer was bioinspired by keratin based porcupine quills which have a cortex sheath wrapped around a closed cell foam. The porous scaffold microstructure was strengthened by infiltration with a dual network hydrogel that bound to phosphate in the hydroxyapatite lamellar walls to make an interconnected composite structure bioinspired by spongy bone.