Lessons from Nature

In examining biological load carriers such as the stems of plants and the trunks of trees, animal bones, mollusk shells, and other biological hard tissues, it can be seen that their geometry changes to accommodate to their physical environment. This implies that they are highly adapted to all boundary and loading conditions defined by their environment. Only the most economical construction is able to survive the intense competition for energy as well as the external physical conditions with the minimal amount of materials available to them in their limited living space. For example, the interior structure (architecture) of a bone has an optimized shape with respect to the direction of principal stress and the magnitude of the shear stress [1]. This has been explained to be due to an optimized mechanical design that is characterized by uniform stress distribution with no localized stress peaks [2]. This suggests that both bone and other biological tissues are managed by a self-optimizing system with sensing mechanisms that can detect external mechanical stimuli in order to control the modeling and remodeling of the skeletal system [3]. It can be inferred, therefore, that the shape and ingenious construction of biological hard tissues are the result of a continuous process of intelligent optimization.