New 3D-printing enables color-changing, stress-responsive materials for smart sensing, displays, and robotics
Penn engineers have developed a transparent silicone shell to preserve cholesteric liquid crystal elastomers—color-changing materials that can respond to mechanical stress—while supporting intricate 3D designs.
2 min. read
A multidisciplinary team, including researchers from Penn’s School of Engineering and Applied Science, has successfully developed a cutting-edge method to 3D print cholesteric liquid crystal elastomers (CLCEs), opening the door to dynamic, color-changing materials that can respond to mechanical stress. This work, published in Advanced Materials, combines advanced printing techniques with unique material properties to pave the way for groundbreaking applications in smart sensing, displays, and robotics. At the heart of this advancement are CLCEs—soft, rubbery materials capable of changing color when subjected to mechanical stress.
Alicia Ng, a Ph.D. student in materials science and engineering holds up an array of different structures made with a new, 3D-printed material that changes color when stretched.
(Image: Penn Engineering Today)
“The color changes are caused by the material’s ability to manipulate light, much like a beetle shell reflects light to create a colorful display,” says Shu Yang, Joseph Bordogna Professor and Chair of Materials Science and Engineering (MSE) and lead investigator of the work. “These materials have the potential to solve industry problems across medicine, diagnostics, monitoring and can even be used in art.”
The team’s innovation centers around a novel 3D printing technique known as Coaxial Direct Ink Writing (DIW), which allows for the precise printing of multi-stable, color-changing structures.
When turning 2D structures into 3D structures, the liquid precursor of the CLCE is so viscous that when pushed through a 3D-printing nozzle it hinders the formation of the twisted helix structures which are responsible for the color-changing characteristics of the CLCEs.
To solve this problem, Alicia Ng, a Ph.D. student in MSE and lead author of the study, and her colleagues set out to find the perfect CLCE viscosity: thick enough to maintain the structural integrity of the finished product but not too thick to allow the material to easily flow through a printing nozzle.
“We developed a transparent silicone shell to serve as a scaffold for the CLCE core,” says Ng. “This unique combination of materials allowed us to preserve the color-changing properties of the CLCEs while providing the necessary structural strength to support intricate 3D designs.”
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