Associate professor Markus Buehler of the Department of Civil and Environmental Engineering, MIT, and co-authors used computer-optimized designs of soft and stiff polymers placed in geometric patterns that replicate nature's own patterns, and a 3-D printer that prints with two polymers at once.
The team produced samples of synthetic materials that have fracture behaviour similar to bone and one of the synthetics is 22 times more fracture-resistant than its strongest constituent material, a feat achieved by altering its hierarchical design.
Buehler said that the geometric patterns they used in the synthetic materials are based on those seen in natural materials like bone or nacre, but also include new designs that do not exist in nature.
The researchers created three synthetic composite materials, each of which is one-eighth inch thick and about 5-by-7 inches in size.
The first sample simulates the mechanical properties of bone and nacre (also known as mother of pearl). This synthetic has a microscopic pattern that looks like a staggered brick-and-mortar wall: A soft black polymer works as the mortar, and a stiff blue polymer forms the bricks.
Another composite simulates the mineral calcite, with an inverted brick-and-mortar pattern featuring soft bricks enclosed in stiff polymer cells. The third composite has a diamond pattern resembling snakeskin. This one was tailored specifically to improve upon one aspect of bone's ability to shift and spread damage.
The team confirmed the accuracy of this approach by putting the samples through a series of tests to see if the new materials fracture in the same way as their computer-simulated counterparts. The samples passed the tests, validating the entire process and proving the efficacy and accuracy of the computer-optimized design.
According to Buehler, the process could be scaled up to provide a cost-effective means of manufacturing materials that consist of two or more constituents, arranged in patterns of any variation imaginable and tailored for specific functions in different parts of a structure.
He is hoping that eventually entire buildings might be printed with optimized materials that incorporate electrical circuits, plumbing and energy harvesting.
The paper has been published online in Advanced Functional Materials.
--ANI (Posted on 19-06-2013)