Search

Structural integrity and robustness are key parameters to evaluate microfabrication techniques. Bending and collapsing of 2D/3D microstructures are commonly noted in solvent-involved procedures, e.g., liquid-based post-treatment in wet-etching, lithography, and Two Photon Polymerizations (TPPs). Such structural failures are caused by excessive solution-imposed capillary forces, where multiple kinds of liquids may intensively participate. Current pieces of the literature focus on the mechanical one-axis models to illustrate their deformation process. To date, there exists an emerging demand for dual-axis models to satisfy rapidly developed micro/nano-engineerings. Here, utilizing polymer micro-pillars distributed in a square array as an illustration example, a dual-axis beam-sway model is proposed considering the influences of structure arrangement as well as the solvent. Specifically, a simplified criterion for judging structural stability is identified. For verifications, the TPP-based experimental data show excellent consistency with model predictions. All in all, the extended model offers reliable guidance for the fabrication of delicate structures and further benefits the optimization of related microfabrication processes. [ABSTRACT FROM AUTHOR]

Springs are ubiquitous in a variety of scientific and engineering fields. However, the comprehensive study on mechanical properties of micro-spring has not been fully conducted yet due to a lack of reliable productions of varied-shaped micro-springs. Here, we report the design and manufacturing of triple-helix-shaped springs employing two-photon polymerization (TPP) technologies and present a systemic study on the mechanical properties of micro-springs particularly involving spring constants of k. To construct high-quality hollow microstructures, we optimize the TPP process by combining violet light post-treatment with a proper selection of cleaning liquid. Consequently, we demonstrate that the sensitives k can be actively tuned over a range of two orders of magnitude, from ∼1.5 to ∼108.2 μN/μm while maintaining a high resolution of ∼1 μN/μm. Furthermore, compression tests showcase an excellent agreement among all force-vs-displacement lineshapes, resulting in a small k fluctuation of <1%. On the whole, we expected that the modified TPP technique along with proposed helical springs opens an alternative avenue toward micro-scale force detection, leading to potential applications in the field of bio-sensing, where typical forces to be measured exist within a broad range from several piconewtons to several micronewtons. [ABSTRACT FROM AUTHOR]

Highlights: A facile and generalized design strategy of polymer precursor inks was developed for direct ink writing of metal oxide into submicron 3D architectures. The Maillard reaction between polyethyleneimine and glucose endows the 3D-printed precursors with the excellent shape fidelity during high-temperature pyrolysis. As-printed 3D periodic dielectric structure with woodpile geometry shows a significant light-matter effect in mid-infrared region. Three-dimensional-structured metal oxides have myriad applications for optoelectronic devices. Comparing to conventional lithography-based manufacturing methods which face significant challenges for 3D device architectures, additive manufacturing approaches such as direct ink writing offer convenient, on-demand manufacturing of 3D oxides with high resolutions down to sub-micrometer scales. However, the lack of a universal ink design strategy greatly limits the choices of printable oxides. Here, a universal, facile synthetic strategy is developed for direct ink writable polymer precursor inks based on metal-polymer coordination effect. Specifically, polyethyleneimine functionalized by ethylenediaminetetraacetic acid is employed as the polymer matrix for adsorbing targeted metal ions. Next, glucose is introduced as a crosslinker for endowing the polymer precursor inks with a thermosetting property required for 3D printing via the Maillard reaction. For demonstrations, binary (i.e., ZnO, CuO, In2O3, Ga2O3, TiO2, and Y2O3) and ternary metal oxides (i.e., BaTiO3 and SrTiO3) are printed into 3D architectures with sub-micrometer resolution by extruding the inks through ultrafine nozzles. Upon thermal crosslinking and pyrolysis, the 3D microarchitectures with woodpile geometries exhibit strong light-matter coupling in the mid-infrared region. The design strategy for printable inks opens a new pathway toward 3D-printed optoelectronic devices based on functional oxides. [ABSTRACT FROM AUTHOR]