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Spotlight Profile on Mulalo Doyoyo
Professor Doyoyo leads a group that is conducting groundbreaking and highly innovative research on different types of micro-assembled structures, including “lattice materials”. This research on lattice materials is having a significant impact on various industries that are investigating the use of lightweight “small-scale” structures for future engineering systems and modernized civil infrastructures.
In particular, Professor Doyoyo believes that numerous benefits may be derived from lattice materials because they can be engineered to perform many desired functions such as acting as “smart”, “active” and adaptive structures. Their topologies originate from the interconnected networks of structural elements (such as trusses, shells, cables) in spacefilling polyhedra. Nature constructs materials the same way. For example, inorganic close-packed crystals are fully represented by polyhedra. Because nano- and micro-scale lattices can be and have been fabricated, the utilization of these materials spans several length scales. Interest in these structures will continue to grow because they meet the demands of modern engineering technologies requiring materials systems that are not only light and multifunctional, but also active and adaptable. Micro-assembled structures will be widely implemented in industry if they are proven to perform cost-effectively and better than conventional materials. However, a complete understanding of their functions, topologies, properties and methods of their manufacture is lacking.
As a result, Professor Doyoyo is developing the mechanics and physics of lattice materials. For example, he has investigated and classified lattices that enhance (1) strength with direct-action or stretch-dominant topologies, (2) cushioning effects with crushable topologies, and (3) smartness with hierarchical topologies. He has engineered two-scale lattices with sacrificial sub-lattices, yielding non-traditional bi-surface failure envelopes. The strength of a multi-scale equivalence of this structure could theoretically approach infinity as the level of sub-structuring increases. He has engineered an “auxetic or anti-rubber” material by converting a convex topology to its reentrant convoluted opposite, giving it a negative Poisson’s ratio property. Unlike conventional materials, the structure becomes synclastic when indented, so that it is an excellent shock- and energy-absorber.
Professor Doyoyo is also using lattice materials to find new solutions for storing highly compressed gases. Of the many problems delaying the gasoline engine-to-fuel cell transition, most critical is not being able to store enough hydrogen in automobiles without sacrificing safety and cabin space and achieving the same driving range and performance as gasoline-powered vehicles. Professor Doyoyo has designed lattices that will reduce the weight and increase strength/durability of traditional pressure vessels while also allowing non-round space-filling tank designs. He has also engineered lattices with zero and negative thermal expansions. Such lattices could be used to construct external-skeletons of scientific probes operating in extreme environments, e.g., “liquid-shell probes” for volcanic, desert, deep-sea, and outer-space environments.
Professor Doyoyo’s research is conducted using inter-disciplinary tools borrowed from different scientific disciplines, including materials science, mechanics, mathematics and physics. In addition to his work on lattice materials, Professor Doyoyo also investigates the development of lightweight materials with non-equilibrium microstructures, such as coal ash composites, foamed metals and metallic honeycombs.
More information about Dr. Doyoyo can be found on his CEE faculty page.