This award by the Biomaterials Program in the Division of Materials Research to University of Oregon Eugene is to study the mechanical and material adaptations that have evolved in small organisms to cope with the scaling rule on the whole-tool, and at ultrastructural and molecular scales. When a farmer's harvesting tools get dull, they can be sharpened or replaced. However, these options are not available to many animals. They must rely on tools that are doomed to become less efficient with each use. This is especially problematic for small animals like spiders and insects that rely on the sharpness of their tools to overcome the force limitations associated with their size. It may be that the strange materials, containing up to 25% of zinc, iron, copper, manganese, iodine and bromine that are found in the teeth, jaws, claws and blades of many small animals have evolved to meet this challenge by reducing wear and fracture. This project will study the properties of these materials, with a detailed investigation of their composition. New understanding may be learned from these materials that have evolved in small organisms to meet their distinctive challenges associated with small-scale mechanical interactions. Furthermore, similar materials may find application in sharp tools such as medical devices (e.g. scalpels and miniature "robots"), atomic force microscopy tips, or in other applications that require hard but impact resistant materials. The project will provide great opportunities for research education because it is so interdisciplinary, combining methods from material science, biology, chemistry and physics. This research will be integrated with teaching and training graduate and undergraduate students in this interdisciplinary area.
Sharper tools enable smaller animals (and small, force-limited machines) to cut and puncture the same materials as their larger and stronger counterparts. A mosquito and a lion both puncture the same skin, a sloth and a leaf cutter ant must both cut the same leaves. But as the tool radius gets smaller, the energy required to fracture the tool gets smaller and faster than the energy required to puncture the membrane with the tool, making fracture increasingly likely. The proposers will study the mechanical and material adaptations that have evolved in small organisms to cope with this scaling rule on the whole-tool, ultrastructural, and molecular scales. The proposed activity will: 1) test, for the first time, the mechanical properties of several Heavy Element Biomaterials (HEBs) used in mechanical structure in small animals; 2) test a novel scaling rule suggesting that smaller animals need more fracture resistant tools; 3) begin to test the novel hypothesis that heavy atoms can be used to lower molecular resonant frequencies and thereby damp the high frequency vibrations from impact; 4) test the hypothesis that variations in water binding are correlated with the balances of hardness and fracture resistance in HEBs; 5) test predictions of the balance of mechanical properties in particular HEBs, based on their locations in biological tools; and 6) test a specific zinc binding hypothesis. The researchers of this award will use tools that they have developed or will be developing for measuring mechanical properties of small specimens, as well as advanced chemical techniques such as Atom Probe Tomography. This project will provide research training in these cutting edge technologies as well as gain expertise in interdisciplinary research. Underrepresented and nontraditional students will actively recruited and mentored, and will provide opportunities to participate in this research through an internship program with a local community college. Graduate and undergraduate students will receive research training in a course developed from the outcome of this project.
