Saturday, May 8, 2021

Mighty Morphing Materials Take Complex Shapes

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Troy Oakes
Troy was born and raised in Australia and has always wanted to know why and how things work, which led him to his love for science. He is a professional photographer and enjoys taking pictures of Australia's beautiful landscapes. He is also a professional storm chaser where he currently lives in Hervey Bay, Australia.

Rice University scientists have created a rubbery, shape-shifting material that morphs from one sophisticated form to another on demand. The shapes programmed into a polymer by materials scientist Rafael Verduzco and graduate student Morgan Barnes appear in ambient conditions and melt away when heat is applied. The process also works in reverse.

The smooth operation belies a battle at the nanoscale, where liquid crystals and the elastomer in which they’re embedded fight for control. When cool, the shape programmed into the liquid crystals dominates, but when heated, the crystals relax within the rubber band-like elastomer, like ice melting into water.

In most of the samples Barnes has made so far — including a face, a Rice logo, a Lego block, and a rose — the material takes on its complex shape at room temperature, but when heated to a transition temperature of about 80°C (176°F), it collapses into a flat sheet. When the heat is removed, the shapes pop back up within a couple of minutes.

As fanciful as this seems, the material shows promise for soft robots that mimic organisms and in biomedical applications that require materials that take pre-programmed shapes at body temperature. The research is described in the Royal Society of Chemistry journal Soft Matter.

“These are made with two-step chemistry that has been done for a long time,” said Verduzco, a professor of chemical and biomolecular engineering and of materials science and nanoengineering, adding:

The liquid crystal state is easiest to program, he said. Once the material is given shape in a mold, five minutes of curing under ultraviolet light sets the crystalline order. Barnes also made samples that switch between two shapes, saying:

The lab’s next target is to lower the transition temperature. “Activation at body temperature opens us up to a lot more applications,” Barnes said. She said tactile smartphone buttons that appear when touched or reactive braille text for the visually impaired are within reach.

She’d also like to develop a variant that reacts to light rather than heat. “We want to make it photo-responsive,” Barnes said, adding:

Provided by: Rice University [Note: Materials may be edited for content and length.]

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