The Discovery, Manufacture and Deployment of Advanced Materials

Scientists headed by CEE Professor Oscar Lopez-Pamies have derived the governing equations that explain and describe the macroscopic mechanical behavior of elastomers packed with liquid inclusions directly concerning their microscopic behavior.

Oscar Lopez-Pamies. Image Credit: University of Illinois Urbana-Champaign

The study is explained in an article by Lopez-Pamies and Ph.D. student Kamalendu Ghosh recently reported in the Journal of the Mechanics and Physics of Solids.

This work was performed as part of Lopez-Pamies’s grant from the National Science Foundation (NSF) program, Designing Materials to Revolutionize and Engineer our Future (DMREF).

DMREF is known as a part of the multi-agency Materials Genome Initiative, which aims to set the stage for the breakthrough, manufacture, and deployment of advanced materials.

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, 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. The focus has been almost exclusively on solid filler inclusions.

Oscar Lopez-Pamies, Study Corresponding Author, Department of Civil and Environmental Engineering, University of Illinois Urbana–Champaign

Recent experimental and theoretical outcomes have demonstrated that rather than the addition of solid inclusions to elastomers, liquid inclusions might result in an even highly exciting new class of materials. This has the ability to allow a range of new technologies.

For example, elastomers filled with liquid metals, ferrofluids, and ionic liquids thereby displaying special combinations of physical and mechanical properties.

The reason behind such novel properties is twofold. On one hand, the addition of liquid inclusions to elastomers increases the overall deformability. This is in contrast to the addition of conventional fillers which, being made of stiff solids, decreases deformability.

Oscar Lopez-Pamies, Study Corresponding Author, Department of Civil and Environmental Engineering, University of Illinois Urbana–Champaign

Lopez-Pamies added, “Additionally, the mechanics and physics of the interfaces separating a solid elastomer from embedded liquid inclusions, while negligible when the inclusions are large, may have a significant and even dominant impact on the macroscopic response of the material when the particles are small.”

Strikingly, the equations establishing that these materials behave as solids, albeit solids with a macroscopic behavior that depends directly on the size of the liquid inclusions and the behavior of the elastomer/liquid interfaces,” continued Lopez-Pamies.

Lopez-Pamies concluded, “This allows access to an incredibly large range of fascinating behaviors by suitably tuning the size of the inclusions and the chemistry of the elastomer/liquid interfaces. One such remarkable behavior is ‘cloaking,’ when the effect of the inclusions can be made to disappear.”

Journal reference:

Ghosh, K. & Lopez-Pamies, O. (2022) Elastomers filled with liquid inclusions: theory, numerical implementation, and some basic results. Journal of the Mechanics and Physics of Solids.


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