Colors of crystals, pigments, metals, salt solutions and bioluminescence occur in nature due to the optical properties of electrons in atoms and molecules. However, colors can also result from interference effects on nanostructures. In contrast to artificial coloration, which are caused by well-defined regular structures, the structural colors of living organisms are often more intense and almost angle-independent. In this paper, we report the successful manufacturing of a lamellar nanostructure that mimics the ridge shape of the Morpho butterfly using a 3d-direct laser writing technique. The viewing angle dependency of the color was analyzed via a spectrometer and the structure was visualized using a scanning electron microscope. The generated nano- and micro-structures and their optical properties were comparable to those observed in the Morpho butterfly.

Lasers are instrumental in enabling precise processing and fostering the development of new technologies. Particularly, ultrafast lasers, due to their unique interaction with matter, can achieve not only exceptional spatial precision but also meticulously determine the degree of modification. A prime example of this is laser‐based 3D printing through multi‐photon lithography (MPL). This approach remarkably enables the printing of true 3D structures at the micro‐ and nanoscale, without the need for masks or cumbersome tools, simply by using computer‐aided designs. Owing to these unique capabilities, MPL has emerged as a powerful manufacturing technique across various multidisciplinary fields. The ongoing growth in MPL's utilization has led to notable advancements in printing highly complex structures on different substrates, as well as improvements in resolution and throughput, and the development of novel photosensitive materials, which impressively facilitated MPL's expansion into broader fields over the last few years. In this perspective article, the aim is to highlight these advancements and recent trends in MPL. The current challenges of MPL will be explored, which need to be addressed to ensure its further integration into advanced Additive Manufacturing at the micro‐ and nanoscale. The future perspectives and opportunities of MPL as a laser‐based 3D printing approach will also be discussed.

A successful realization of photonic systems with characteristics of the Morpho butterfly coloration is reported using two-photon polymerization. Submicron structure features have been fabricated through the interference of the incident beam and the reflected beam in a thin polymer film. Furthermore, the influence of the lateral microstructure organization on the color formation has been studied in detail. The design of the polymerized structures was validated by scanning electron microscopy. The optical properties were analyzed using an angle-resolved spectrometer. Tunable angle-independence, based on reflection intensity modulation, has been investigated by using photonic structures with less degree of symmetry. Finally, these findings were used to demonstrate the high potential of two-photon polymerization in the field of biomimetic research and for technical application, e.g. for sensing and anti-counterfeiting.

In this Letter, we investigate the resolution of two-photon polymerization (2PP) with an amplified mode-locked external cavity diode laser with adjustable pulse length and a high repetition rate. The experimental results are analyzed with a newly developed 2PP model. Even with low pulse peak intensity, the produced structural dimensions are comparable to those generated by traditional 2PP laser sources. Thus, we show that a compact monolithic picosecond laser diode without amplification and with a repetition rate in the GHz regime can also be applied for 2PP. These results show the high application potential of compact mode-locked diode lasers for low-cost and compact 2PP systems.

This paper describes how two-photon polymerization was used to generate biomimetic nanostructures with angle-insensitive coloration inspired by the blue butterflies of Morpho. Less angle dependence was achieved by engineering the structures with a certain degree of disorder, which delimited them from classical photonic crystals. Variations in the processing parameters enabled the color hue to be controlled. In this context, blue, green, yellow, and brown structures were demonstrated. Reflection spectra of the structures were simulated and studied experimentally in a broad range of incident angles. Additionally, a molding technique was performed as a potential scale-up strategy. The application of such biomimetic structures is discussed.