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Live heart cells make this material shift color like a chameleon

The hydrogel-based strips change hues when contracting and expanding

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2:00pm, March 28, 2018
chameleon material

KEEPING THE BEAT  Five hydrogel strips covered in heart tissue contract when the heart cells do. That shrinkage makes the material reflect more blue light. When the cells relax, the strips extend and reflect more red light.

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To craft a new color-switching material, scientists have again taken inspiration from one of nature’s masters of disguise: the chameleon.

Thin films made of heart cells and hydrogel change hues when the films shrink or stretch, much like chameleon skin. This material, described online March 28 in Science Robotics, could be used to test new medications or possibly to build camouflaging robots.

The material is made of a paper-thin hydrogel sheet engraved with nanocrystal patterns, topped with a layer of living heart muscle cells from rats. These cells contract and expand — just as they would inside an actual rat heart to make it beat — causing the underlying hydrogel to shrink and stretch too. That movement changes the way light bounces off the etched crystal, making the material reflect more blue light when it contracts and more red light when it’s relaxed.

This design is modeled after nanocrystals embedded in chameleon skin, which also reflect different colors of light when stretched (SN Online: 3/13/15).

When researchers treated the material with a drug normally used to boost heart rate, the films changed color more quickly — indicating the heart cells were pulsating more rapidly. That finding suggests the material could help drug developers monitor how heart cells react to new medications, says study coauthor Luoran Shang, a physicist at Southeast University in Nanjing, China. Or these kinds of films could also be used to make color-changing skins for soft robots, Shang says.

Citations

F. Fu et al. Bioinspired living structural color hydrogels. Science Robotics. Published online March 28, 2018. doi: 10.1126/scirobotics.aat3911.

Further Reading

M. Temming. Watch this cuttlefish-inspired ‘skin’ morph into a 3-D shape. Science News. Vol. 192, November 11, 2017, p. 5.

B. Mole. Nanocrystals explain chameleons’ color shifts. Science News Online, March 13, 2015.

M. Rosen. Chameleon-like robot can change hue. Science News. Vol. 182, September 22, 2012, p. 9.

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