A new publication from Opto-Electronic Advances reviews laser additive manufacturing of Si/ZrO2 tunable crystalline phase 3D nanostructures.

A route for laser nano-printing of 3D crystalline structures was developed employing ultrafast laser lithography, used as additive manufacturing tool for producing true 3D nanostructures, and combined with high temperature thermal post-treatment, converting the printed material into fully inorganic substance.

The inter-disciplinary experimental work revealed the potential of tuning the resulting ceramic structure into distinct crystalline phases, such as cristobalite, SiO₂, ZrSiO₄, m-ZrO₂, t-ZrO₂. The proposed approach achieved below 60 nm for individual feature dimensions without any beam shaping or complex exposure techniques, thus making it reproducible with other established standard or custom-made laser direct writing setups. The principle is compatible with commercially available platforms (for instance: Nanoscribe, MultiPhoton Optics, Femtika, Workshop of Photonics, UpNano, MicroLight, and others). Figure 1 graphically summarizes the approach, involved procedure steps, and resulting outcome.

In brief, the validation of the combined laser manufacturing and thermal-treatment technique upgrades the widespread laser multi-photon lithography to a powerful tool enabling additive manufacturing of crystalline ceramics at an unprecedented precision and three-dimensional flexibility. It is a milestone achievement in the ultrafast laser assisted processing of inorganic materials and sets a new high standard for the nanoscale laser 3D photopolymerization, which is no longer bounded to the limitation of just polymer or plastic materials. While biologically derived and plant-based resins are extending applications in biomedicine and life sciences, the production of 3D inorganic nanostructures is opening new scientific technology-oriented research fields and enabling industry to acquire options for the production of 3D nano-mechanics, nano-electronics, micro-optics and nano-photonics, enhanced telecommunication, and sensing chips.

Dr. Darius Gailevičius with Prof. Mangirdas Malinauskas of Laser Nanophotonics Group (Laser Research Center, Physics Faculty, Vilnius University) proposed an approach for laser 3D additive manufacturing of nanoscale structures out of inorganic materials. The laser-printed objects were subsequently heat treated in order to completely remove the organic part of the hybrid material, thus converting the substance into pure inorganic matter. The aforementioned group members collaborating together with a material scientist Prof.Simas Šakirzanovas (Department of Applied Chemistry, Faculty of Chemistry and Geosciences, Vilnius University) anticipated the potential of sol-gel synthesis and chemical morphing of the substance into diverse and tunable phases by precisely controlling the initial ingredient ratio and the calcination processing protocol. The main experimental work was performed by Ph.D. student Greta Merkininkaitė with assistance of junior student Edvinas Aleksandravičius. A post-doc Dr. Darius Gailevičius has introduced essential conceptual insights and reviewed the experimental workflow.

The findings are important to a whole spectrum of scientific research and industrial fields. It extends the widespread established laser two-photon polymerization technology towards additive manufacturing of ceramic and crystalline structures at a sub-100 nm feature definition. This makes the previous limitation of the employed organic or hybrid polymers obsolete. It also enables production of inorganic and tunable crystalline phase 3D nanostructures, which are outperforming the previously available material choices or limited structural (2D or 2.5D geometries) flexibility.

In other words, the optical 3D printing is now offering additive manufacturing of various crystals. The principle is advantageous in making three-dimensional nano-photonic, micro-optical, nano-mechanic, micro-fluidic, nano-electronic and bio-medical components. It upgrades the laser 3D nanoscale printer from black and white into a full color, as the colors are represented by specific material and its inherent properties. In Figure 2 continuous scaling and material variations are visually projected. A novel option of true 3D printing inorganic materials is a benchmarking milestone achievement—upgrading the existing laser 3D lithography to a new exploitation level.

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