Tuesday, February 14, 2006

Biomimicking: Engineering Design from Natural Structures

By M. Bowman, Sarah Darkwa, and Adam Davison

            Dr. Lorna Gibson, Professor of Materials Science and Engineering at MIT, presented her research on Biomimicking: Engineering Design from Natural Structures at ESF on Tuesday, February 14, 2006 as part of SUNY ESF's Women in Scientific and Environmental Professions Spring Seminar Series. The ESF Women’s Caucus and the Faculty of Environmental Resources and Forest Engineering jointly sponsored the seminar.
Dr. Gibson discussed naturally occurring structures in plants and animals in terms of how they provide flexural rigidity and resist critical loading.  In other words, how the structures provide both strength and flexibility without overly increasing weight of the animal or significantly reducing photosynthetic capacity of the plant. 
These structures fall into several categories: iris and cattail leaves are structural sandwich panels, while plant stems, bluejay feathers, and porcupine quills are cylindrical shells with compliant cores. Both types of structures are comprised of fibers or a dense shell on the outside with a foam core on the inside.  Sandwich panels are typically a low-density core material sandwiched in between two higher modulus plates, which allows for a lightweight structure with a high rigidity and load capability. Skis and helicopter rotor blades are similarly constructed to reduce their weight without compromising their strength.  The compliance of the core material provides resistance in all directions, which allows stems to resist and prevents bird feathers from kinking.
Other efficient structures for load resistance are represented by palm trees, bamboo, and woods such as oak. Wood in particular has a uniform cylindrical structure or “honeycomb” and is one of the most efficient at resisting loads. The gradient structure of palm trees and bamboos that allows the stems to grow taller without adding diameter at the ground level had a large influence on the engineering of bone scaffolds.
The scaffold that Dr. Gibson and her colleagues are working on is mineralized collagen foam that is comprised of different gradients. This scaffold is particularly useful for joint implants, since joints are an interface of bone and cartilage. So far they have tested their scaffolds in the joints of sheep and goats with very promising results for human use.
Professor Lorna J. Gibson received her Bachelor of Applied Science degree in Civil Engineering from the University of Toronto in 1978 and her PhD from the University of Cambridge in 1981. She was an Assistant Professor in the Department of Civil Engineering at the University of British Columbia from 1982-84. She joined the MIT faculty in 1984, where she is currently the Matoula S. Salapatas Professor of Materials Science and Engineering. Her research interests focus on the mechanical behavior of highly porous materials with a cellular structure, such as engineering foams, trabecular bone and scaffolds used in tissue engineering. She is the co-author, with Professor M.F. Ashby, of the book "Cellular Solids: Structure and Properties". She has been active in MIT’s gender equity efforts, chairing the Committee on Women Faculty in the School of Engineering.  The next presentation in the Women in Scientific and Environmental Professions speaker series is March 28.  Nancy Grulke, Project Leader, Atmospheric Deposition on Western Ecosystems and plysiological ecologist, Pacific Southwest Research Station, will discuss “Air pollution and the Californian wildfires:  an insidious link” at 4 pm in 140 Baker Laboratory.  For more information, visit http://www.esf.edu/womenscaucus. 

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