A research team at the University of Pennsylvania has developed a new method for processing cholesteric liquid crystal elastomers (CLCEs) in 3D printing. The study, published in Advanced Materials, describes a process that enables mechanically responsive, color-changing structures. By using Coaxial Direct Ink Writing (DIW), CLCEs could be transformed into complex 3D geometries for the first time without losing their optical properties.
CLCEs are soft, rubber-like materials that can change their color depending on mechanical stress. The effect is based on the interaction with light through an internal, helical microstructure – comparable to the reflective surface of beetle shells. This property makes them interesting for applications in sensor technology, robotics, medical technology and interactive displays. However, processing in 3D has so far been a challenge, as the high viscosity of the CLCE precursor impaired the formation of the helical structure required for the color change.
Alicia Ng, PhD student in materials science and first author of the study, developed a new printing concept together with the team. The CLCE material core is surrounded by a transparent silicone shell. This serves as a structural framework and makes it possible to maintain the desired shape while retaining the optical properties of the material.
“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.”
“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.”
3D printing technology allows not only targeted shaping, but also the integration of color-changing properties into sustainable, complex structures – an advance with technological potential for various industries.
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