Biomimetics: Creating Materials From Nature's Blueprints

Biomimetics: Creating Materials From Nature's Blueprints AUTHOR: ROBIN EISNER, P.14 In order to design a 21st-century, impact-resistant substance, materials scientist Mehmet Sarikaya of the University of Washington in Seattle finds inspiration in a 500-million-year-old feat of evolution--the shell of a present-day mollusk, the abalone. Following blueprints drawn from analysis of the microarchitecture of the shell, Sarikaya and colleague Ilhan Aksay have manufactured a prototype material that mimics the shell's laminar, protection-providing structure. Sarikaya is one of growing number of materials researchers involved in biomimicking, or biomimetics--the study of the structure and function of biological materials and systems as models for materials design. According to materials scientist Aksay, also from the University of Washington, about 500 scientists in the United States are involved in some aspect of biomimicking, although they might not identify their specialty as such. What they have in common is looking at nature as a guide to create the materials for the new machines, fabrics, and shelters of the next century. While biomimicking, per se, represents a small part of the federal government's current resurgence of interest in materials research, these scientists see their approach as crucial to the national technology development effort and as a source of opportunities for collaborations involving academic, industrial, and government scientists in disciplines as diverse as botany, aerospace, and condensed-matter physics. Proponents of biomimetics say there are numerous economic, environmental, and scientific advantages to be gleaned from their approach to materials design. Sarikaya says that when the time comes to actually develop materials based on the biomimetic paradigm, around 15 to 20 years from now, "we will most likely use raw materials that are cheaper; energy costs will be lower, since many of the processes in nature take place at room temperature; and, to some extent, these materials we make will be biodegradable." But the material, based on the shell, that Sarikaya and Aksay created in their laboratory at the University of Washington--a carbon, boron, and aluminum mixture--is not as tough or strong as they believe it can be. Although their new material is better than a similar substance composed of these elements, it is still not as good as the shell in these parameters. Sarikaya and Aksay's material tested 1.3 times tougher and stronger than the standard carbon, boron, and aluminum mixture. But the shell's protein-and-calcium-carbonate-layered structure has hundred-fold superiority to the strength and toughness of its standard of comparison, calcium carbonate--the inorganic salt that makes up 98 percent of the shell--alone. Since the scientists cannot directly measure their new material against the shell for these characteristics, because it would be like comparing apples and oranges, they must compare these magnitudes of difference. They are still off by at least a factor of 10. To increase the toughness and strength of their biomimetics-produced material, they think they will have to make the component layers of their substance thinner. The mollusk somehow exudes its protein in a layer that is two hundred-millionths of a meter thick and places it upon a five ten-millionths of a meter layer of calcium carbonate. The University of Washington group can achieve thicknesses only on the order of a hundred-thousandth of a meter. Eventually, though, the group expects to overcome this limitation by layering both biologic and synthetic materials during manufacture. According to researchers working in this area, the collaborations that are necessary for biomimetics to be successful will generate advances for all the scientific disciplines concerned. Biologists, for example, will ask more fundamental questions about the nature of the organisms and systems they study in order to answer the questions that the chemists, physicists, and engineers pose when they do materials design. "Biologists and technologists are finally coming to the realization that there is something to be gained by seriously working together," says Stephen Wainwright, a mechanical biologist at Duke University. Sarikaya adds: "There is no way a materials scientist will be able to do it on his or her own." Armutur Srinivasan, aerospace engineer at United Technologies in Hartford, Conn., and coeditor of Biomimetics, a journal that Plenum Press in New York expects to launch in the spring of 1992, says biomimetics will spawn new kinds of scientific instruments and approaches to materials manufacturing. "To truly understand materials in nature, we have to see them in their living state," he says. "Most of the measurements we make are unnatural, based on dead material. This field offers opportunities to design machines that can monitor life better. And once we understand how materials are made in living systems, we can then mimic the processes artificially and efficiently." J. Currey, "Biological Composites," Journal of Materials Education, 9[1-2]:118-296, 1987. E. Baer, A. Hiltner, H.D. Keith, "Hierarchical Structure in Polymeric Materials," Science, 235:1015-22, 1987. L. Addadi, S. Weinder, "Interaction between Acidic Proteins and Crystals: Stereochemical Requirements in Biomineralization," Proceedings of the National Academy of Sciences, 82:4110-14, 1985. S. Mann, et al., "Controlled Crystallization of CaCO3 Under Stearic Acid Monolayers," Nature, 334:692-95, 1989. Wainwright says that biological materials and systems are multifunctional, adaptive, nonlinear, complex, and, in general, just "weird and wonderful" compared to somewhat simplistic synthetically created materials. Bone, for example, is far more complicated than metals, according to Srinivasan, and possesses remarkable abilities of structural adaptation to external loading. Bone differs not only from animal to animal, but also from place to place within the same animal. It changes over time, and under various loading conditions. Wainwright says biomimetics is the single most exciting thing in science he has experienced in his life. "And I am turning 60 this year," he says. Since biological form and function will be the key to materials design, Wainwright feels that descriptive biology, the study of the structure of biological systems, will overcome its current poor reputation as a dead, 19th-century science. "It's going to take a lot of morphologists [descriptive biologists] out of the ivory tower of basic research into the area of applied research. It will open many doors for them," he says. But the main disadvantage of this kind of research is related to its very advantage: Most biological systems operate at room temperature and pressure, and often in aqueous environments that aren't good for, say, aerospace or extreme applications. "Jet engine parts function at 2,000 F," says Srinivasan. "The challenge for materials scientists is to learn from biological systems and modify the chemistry so we can benefit. Some people think we cannot do it." Another concern of biomimics is that too much publicity about the field will arouse unrealistic expectations of quick success by governmental, academic, and industrial research grant providers. "If they expect results and they don't happen, they will get disenchanted, cut back on funding, and hurt the people really interested in the field," says Aksay, who, along with Sarikaya, organized a three-day conference in Seattle in April on "Design and Processing of Materials by Biomimicking," sponsored by the Air Force Office of Scientific Research. "But this field will only reach maturity after many years of work," Aksay says. He worries that the field could suffer the same problems that superconductivity did. "Publicity will make people expect products to be rolling out of the manufacturing plant in the next four to five years. But the real scientists know it takes much longer than that." Aksay's concern is timely. Biomimickry is part of a larger effort among U.S. scientists and policymakers to develop a strong, economically competitive materials research program in the U.S. This past April, after many high-level meetings and a National Research Council report, the Office of Science and Technology Policy (OSTP) in the White House announced its plan to coordinate and make new monies available for materials research in the country. All the agencies that have a stake in this initiative, which will be administered by the OSTP's Federal Coordinating Council on Science, Engineering and Technology (FCCSET), are in the process of providing their budgetary and scientific input to this executive-level office. Analogous multiagency initiatives currently administered by FCCSET coordinate high-performance computing and education in the U.S. For materials, "each agency is driven by different needs," says Aksay. "The Department of Energy, for example, is concerned about environmentally conscious materials processing. They are looking for materials and processes that are energy- conserving, nonpolluting, and recyclable. The Department of Defense, on the other hand, is interested in materials for weapons and for the Air Force. They are interested in airplanes that can lift off without a runway. The Navy wants materials that will protect their ships from corrosion. The National Institutes of Health want biomaterials that have medical applications." Although the OSTP materials program will be included in the president's 1993 budget, the National Science Foundation has gotten a jump start in this initiative in the agency's 1992 budget. According to Jim Brown, division director of molecular biosciences at NSF, the agency expects an additional $25 million for materials research in 1992 over its 1991 allocation of $59 million. Of that new money, some $7 million to $9 million is slated for biomimicking-related research. In late March, the foundation sent out letters announcing the funds to 5,000 scientists. "We hoped to generate the development of collaborations for eventual proposal submissions," says Brown. The same day that the OSTP made its announcement, the two senators from New Mexico, Democrat Jeff Bingaman and Republican Pete Domenici, introduced the Advanced Synthesis, Processing and Commercialization Act, which would provide $475 million over the next five years for materials research partnerships among industry, academia, and federal laboratories. The bill allots an additional $474 million for university-based efforts exclusively. In late June, the Technology and Competitiveness Subcommittee of the House Committee on Science, Space, and Technology held a hearing focusing on ways to beef up materials science in the U.S. Among the issues the committee discussed with leaders in materials research were the status of materials technology, the consequences of foreign domination in this field, the question of involvement of federal labs in joint ventures with industry; and whether regulatory and safety concerns are impeding the development and commercialization of materials in the U.S. Says a staffer on the subcommittee: "Materials are essential for the economic viability and competitiveness of American industry. If the U.S. loses out on this, which is the cornerstone for numerous other industries in the U.S., we are in trouble." And according to materials scientist Aksay, biomimicking will play a critical role in keeping America's edge.

Biomimetics: Creating Materials From Nature's Blueprints

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