Researchers Develop Quick Test for Materials Properties

By Anonymous

Analyzing the mechanical properties of 600 different materials takes weeks using conventional techniques. Researchers at the Massachusetts Institute of Technology (MIT) have developed a process that yields this data in 24 hours, using small samples and nanoindentation. The project began as an experiment using biomaterials in MIT’s Chemical Engineering Department. In 2004, researchers used robotic technology to deposit more than 1.700 spots of 500 different biomaterials on a glass slide measuring 25 mm wide by 75 mm long. Twenty of these slides, or microarrays. could be made in a single day. The arrays were used to determine which materials were most conducive to the growth and differentiation of human embryonic stem cells.

Krystyn J. Van Vliet of the MIT Department of Materials Science and Engineering collaborated with Daniel G. Anderson of MIT’s Department of Chemical Engineering to show that the mechanical properties of each biomaterial could be determined by combining the arrays with nanoindentation. In nanoindentation, a hard, small probe is pressed into a more compliant material, to depths many times smaller than the diameter of a human hair. By measuring the force applied and how deeply the probe penetrates the material, scientists can learn a great deal about the material’s mechanical properties.

The team created new arrays of roughly 600 unique polymers to use with the nanoindentation process. “Each dot was a combination of two different monomers, or building blocks, so we could map out the effects of the percentage of each monomer on the properties of the material,” said Van Vliet. In 24 hours, the researchers had data from the samples in hand. In this first experiment, researchers discovered some surprises in material behavior.

“The stiffness of certain polymers depended more on the combination of monomers used (how much of A and B) rather than the structure of each monomer, with certain combinations resulting in very compliant polymers,” said Catherine A. Tweedie, a graduate student in material science and engineering who worked on the project. “These were very large, unanticipated changes in mechanical properties that could then be optimized further in a subset of combinations.”

The research was published in November’s issue of Advanced Materials.

Copyright Minerals, Metals & Materials Society Jan 2006