Two-photon polymerization as a potential manufacturing tool for biomimetic engineering of complex structures found in nature

We report on the successful use of three-dimensional (3D) printing by two-photon polymerization to engineer optimized hierarchically composed surface structures at the micro- and nanoscale. The hierarchical composition of the printed structures was inspired by those found on the upper wing surface of blue-winged butterflies from the genus Morpho. In this way, the nanostructures and blue coloration of the organisms was mimicked, but less iridescence was achieved for biomimetic surfaces. Like the biological surface structures, the ones printed exhibited disorders characteristics. As a result, the blue colors generated by biomimetic structures displayed angle-insensitive optical properties similar to those of the Morpho wings. In addition, the great design freedom and simple workflow of the 3D printing technique enabled the fabrication of different structures at the microscale without modifying the dimension of the substructures at the nanoscale. Thus, it was possible to set the direction in which angle-insensitive coloration appeared to an observer. The morphology of biological and biomimetic surface structures was analyzed and compared using scanning electron microscopy. The optical properties of biological and engineered specimens were determined using angle-resolved spectroscopy. Furthermore, the coloration of biomimetic surfaces and the upper wing surface of Morpho butterfly was studied in different liquids. The results were compared, and potential application for biomimetic surfaces was discussed.