Researchers develop a novel theory about how a new class of materials behaves.

 

The governing equations that define and explain the macroscopic mechanical behavior of elastomers filled with liquid inclusions directly in terms of their microscopic behavior have been developed by researchers under the direction of Oscar Lopez-Pamies, professor of CEE. A recent publication by Lopez-Pamies and PhD candidate Kamalendu Ghosh in the Journal of the Mechanics and Physics of Solids describes the study.

According to Lopez-Pamies, "efforts have been continuously devoted to understanding when and how the addition of fillers to elastomers lead to materials with novel mechanical and physical properties ever since the discovery in the early 1900s that the addition of carbon black and silica nanoparticles to rubber resulted in a composite material with drastically enhanced properties." "Almost only solid filler inserts have been the focus,"

Recent theoretical and experimental findings suggest that introducing liquid inclusions to elastomers rather than solid ones may result in a new class of materials that is even more intriguing and has the potential to allow a number of new technologies. Examples of materials that display unusual combinations of mechanical and physical characteristics include elastomers filled with ionic liquids, liquid metals, and ferrofluids.

According to Lopez-Pamies, "There are two reasons for such new traits." On the one hand, elastomers' general deformability is increased by adding liquid inclusions. In contrast, the use of typical fillers reduces deformability since they are formed of rigid materials.

 Furthermore, whereas the interfaces between a solid elastomer and embedded liquid inclusions are inconsequential when the inclusions are big, they may have a considerable and even dominant influence on the material's macroscopic response when the particles are small.

"Surprisingly, the equations prove that these materials act as solids, although solids with a macroscopic behavior that is directly influenced by the size of the liquid inclusions and how the elastomer/liquid interfaces function.

 By properly adjusting the size of the inclusions and the chemistry of the elastomer/liquid interfaces, this gives access to an immensely wide range of intriguing behaviors. One such extraordinary behavior is "cloaking," which is the ability to make the effect of the inclusions vanish."

The NSF program, Designing Materials to Revolutionize and Engineer our Future, funded Lopez-Pamies' work on this project (DMREF). The multi-agency Materials Genome Initiative, which aims to open the door for the development, production, and use of new materials, also includes DMREF as a member.