Eindhoven University of Technology (TU/e) scientists have developed a new liquid crystal ink for advanced, rapid production methods like 3D printing.
According to the scientists, their light-reflective (cholesteric) liquid crystal ink is viscous enough to make stable, solid structures, and its molecules can be easily aligned to produce specific colors.
Iridescent materials that change color when viewed from different angles can be found in butterfly wings and in nacre (mother of pearl). A man-made version of these natural materials is cholesteric liquid crystal.
Though these are used as ‘smart’ materials in light reflectors and tunable solar energy collectors, the current manner of producing them remains nonetheless complicated.
Hoping to resolve this, the TU/e team along with Netherlands Organisation for Applied Scientific Research (TNO), Koninklijke DSM, Brightlands Materials Center, and SABIC have developed a liquid crystal elastomer-based ink that can be 3D printed on a surface via Direct-Ink-Writing (DIW).
According to lead author and TU/e PhD candidate Jeroen Sol, the new liquid crystal ink comes with several distinct properties.
First and foremost, the light reflective properties of the ink rely on the precise helical alignment of molecules throughout the material which requires fine tuning of the printing process.
Second, the molecules in the ink can self-assemble into such structures that display colors similar to natural iridescent materials, like those in butterfly wings.
Third, the new ink has greater viscosity than previous inks, which makes it suitable for DIW printing.
What’s more, the new ink is novel, easy to make, easy to process, and based on materials previously developed by the SFD research group at TU/e for light-reflective coatings.
“To successfully print the new ink with DIW, we varied parameters like print speed and temperature,” notes Sol. “And to get the ink to print properly, we also made an ink containing low-molecular weight liquid crystals.”
The scientists – with the help of these variations – used the new ink to successfully print synthetic butterfly wings.
Sol and his teammates were also able to control the nanoscale molecular alignment very accurately by varying the print speed.
This breakthrough helped them to have greater control over the appearance and light reflecting properties of the material.
Image and content: Eindhoven University of Technology