Laser additive manufacturing of Si/ZrO2 tunable crystalline phase 3D nanostructures

The current paper is focused on the rapidly developing field of nano-/micro three-dimensional production of inorganic materials. The fabrication method includes laserlithography of hybrid organic-inorganic materials with subsequent heat treatment lead-ing to a variety of crystalline phases in 3D structures. In this work, it was examineda series of organometallic polymer precursors with different silicon (Si) and zirconium (Zr) molar ratios, ranging from 9:1 to 5:5, prepared via sol-gel method. All mixtureswere examined for perspective used in 3D laser by manufacturing by fabricating nano-and micro-feature sized structures. Their deformation and surface morphology wereevaluated depending on chemical composition and crystallographic phase. The appear-ance of a crystalline phase was proven using single-crystal X-ray diffraction analysis,which revealed a lower crystallization temperature for microstructures compared tobulk materials. Fabricated 3D objects retain a complex geometry without any distortion after heat treatment up to 1400oC. Under the proper conditions, a zircon phase (ZrSiO4 - a highly stable material) can be observed. In addition, the highest newrecord of achieved resolution below 60 nm has been reached. The proposed prepara-tion protocol can be used to manufacture micro/nano-devices with high precision andresistance to high temperature and aggressive environment.

. A graphical summary showing:(a) used raw organic and inorganic precursors, their molar ratios in synthesis;(b) laser photopolymerization and hightemperature calcination technology;(c) formed crystalline phase nano-lattices after calcination (cristobalite, SiO2, zircon, monoclinic ZrO2 and tetragonal ZrO2);All of these phases can be observed and tuned depending on the treatment temperature and initial hybrid materials compositions. Credit: Compuscript Ltd 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, SiO 2 , ZrSiO 4 , m-ZrO 2 , t-ZrO 2 . 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. On the other angle of view, the materials are in full colors, thus resembling: biopolymers and proteins as natural and purely organic resins, hybrid materials offering glass-like properties or composites with enhanced specific functionalities, and finally inorganic substances such as ceramics or crystals. All of it can be realized via laser mesoscale 3D lithography and is a tool for applications in (a) nanophotonics; (b) micro-optics and precision prototyping in microfluidics and micromechanics; (c) bio-scaffolds. Credit: Compuscript Ltd Dr. Darius Gailevi?ius 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 Merkininkait? with assistance of junior student Edvinas Aleksandravi?ius. A postdoc Dr. Darius Gailevi?ius 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 threedimensional nano-photonic, micro-optical, nanomechanic, micro-fluidic, nano-electronic and biomedical 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.