TECHNICAL: Abalone shell is tough and fracture resistant. The structure has a brick-and-mortar organization with calcium carbonate (aragonite) bricks surrounded by the organic mortar. The toughness is attributed to the organized arrangement of the aragonite platelets and nanoscale features present at the mineral/organic interface. These nanoscale features include mineral bridges, nanoasperities on the surface of the aragonite tiles and the viscoelastic/adhesive properties of the organic. The main objectives of this work are to fabricate model ceramic/polymer laminates, identify and quantify the contributions of microstructural features that have been attributed to the toughening of the shell. This work is expected to lead to a new class of bioinspired composite materials that are strong, hard and fracture resistant. Students will be cross-trained in biology, materials science and nanoscience.
NON-TECHNICAL DESCRIPTION: Bioinspired materials are emerging as a new class of synthetic structures. The abalone shell is tough and fracture resistant, despite being built from weak constituents: organic matter and a soft mineral (ceramic). Under magnification, the shell has a "brick-and-mortar" structure of mineral bricks and organic mortar. Bioinspired synthetic layered materials based on this structure are expected to have exceptional toughness and fracture resistance. Fabrication and testing of layered organic (polymer) / ceramic structures that duplicate the structure of the abalone shell is the main focus of research. This work is expected to lead to a new class of composite materials that are strong, hard and fracture resistant. Graduate, undergraduate and high school students will be cross-trained in biology, materials science and nanoscience. New classes will be introduced into the curriculum and outreach to underrepresented student populations is a part of this project.
Structural biological materials such as sea shells, bone and teeth have high strength and fracture resistance, despite being built from relatively weak constituents. The reasons behind these excellent mechanical properties are the ordered structures observed over a range of length scales and the nanoscale features that exist between the constituents. Bioinspired materials development takes design templates from nature to fabricate synthetic materials that have the internal structure of the natural materials but built from strong, tough ceramics and polymers. This project was inspired by the high strength and high fracture resistant nacre in the abalone shell, which has a layered structure of oriented minerals held together by a biopolymer. We developed tough coatings and composite materials (ceramic and polymer) that duplicated this structure. We invented magnetic field-assisted freeze casting, inspired by the spiraling nature of the narwhal tusk, to further strengthen the composites. We extended our investigations into other natural materials, such as the gripping seahorse tail, armored fish scales, porcupine quills, bird bone constructions, feathers and alligator skin. In all of these, we discovered the fundamental deformation and failure modes that were extended into creating bioinspired materials and structures. The bioinspired materials were fabricated using thin film methods, ice templating and additive manufacturing (3D printing). Pubic interest in this research resulted in coverage and images features in over 50 media outlets including Popular Science, ABC News, Discovery News, YouTube, USA Today, Smithsonian Magazine, R&D Magazine, Biomimicry News, Facebook, Google+, LinkedIn, MSN News, The Scientist, Science Daily and United Press International. Four Ph.D.’s were awarded, two of them to women. Two M.S. degrees (thesis) were awarded. Four postdocs were mentored (three were women). Over 60 undergraduates participated in the research, including underrepresented ethnic minorities and women. Outreach to K-12 students was performed, either by hosting student groups or taking our lab demos to their classrooms. Underrepresented high school students worked in the lab during the summer. The undergraduate or graduate students gave 69 presentations at various national and international meetings. Forty one manuscripts were published that included 30 peer reviewed publications and 11 conference proceedings. Additionally a patent disclosure was filed on a bioinspired gripper.
