HOUSTON (Dec. 9, 2013) Heating a sheet of plastic may not bring it to life but it sure looks like it does in new experiments at Rice University.
The materials created by Rice polymer scientist Rafael Verduzco and his colleagues start as flat slabs, but they morph into shapes that can be controlled by patterns written into their layers.
The research is the subject of a new paper in the Royal Society of Chemistry journal Soft Matter.
Materials that can change their shape based on environmental conditions are useful for optics, three-dimensional biological scaffolds and the controlled encapsulation and release of drugs, among other applications, the researchers wrote.
"We already know the materials are biocompatible, stable and inert," Verduzco said, "so they have great potential for biological applications."
The material needs two layers to perform its magic, Verduzco said. One is a liquid crystal elastomer (LCE), a rubber-like material of cross-linked polymers that line up along a single axis, called the "nematic director." The other is a thin layer of simple polystyrene, placed either above or below the LCE.
Without the polystyrene layer bonded to it, an LCE would simply expand or contract along its nematic axis when heated. With changing temperature, the LCE tries to contract or expand, but the stiffer polystyrene layer prevents this and instead causes wrinkling, bending or folding of the entire material.
The lab discovered that the layers would react to heat in a predictable and repeatable way, allowing for configurations to be designed into the material depending on a number of parameters: the shape and aspect ratio of the LCE, the thickness and patterning of the polystyrene and even the temperature at which the polystyrene was applied.
The lab made spiraling, curling and X-shaped materials that alternately closed in or stood up on four legs. Placing polystyrene on top o
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