In nature, iridescent materials, which exhibit a color change when viewed from different angles, can be found in butterfly wings and in nacre (or mother of pearl) in the inner shell of mollusks.

A man-made version of these natural materials is cholesteric liquid crystal, which has already been used as "smart" materials in light reflectors, switchable windows, and tunable solar energy collectors.

For healthcare applications in soft wearable sensors or decorative lighting, cholesteric liquid crystals are ideally suited. Until now though, an easy way of producing these materials and making devices from these materials has been lacking.

Researchers from the department of Chemical Engineering and Chemistry at TU/e in collaboration with TNO, DSM, Brightlands Materials Center (in the DynAM consortium), and SABIC have created a nature-inspired liquid crystal elastomer-based ink that can be 3D printed on a surface via Direct-Ink-Writing (DIW). Lead author for the study is Ph.D. candidate Jeroen Sol, with Albert Schenning and Michael Debije from the Stimuli-responsive Functional Materials and Devices (SFD) group heading the research project.

"DIW is an extrusion-based 3D printing approach where an ink is dispensed from a small nozzle onto a surface on a layer-by-layer basis. Current cholesteric liquid crystal inks cannot be printed with DIW, so we created a liquid crystal ink compatible with DIW," says Sol.