Ordered growth of metal oxides in patterned multi-angle microstructures.

Herein, we report a facile method combining top-down patterning transfer and bottom-up nanorod growth for preparing large-area and ordered TiO2 nanorod arrays. Pre-crystallization seeding was patterned with nanostructured morphologies via interfacial tension-driven precursor solution scattering on various types and period templates. This is a widely applicable strategy for capillary force-driven interfacial patterns, which also shows great operability in complex substrate morphologies with multiple-angle mixing. Moreover, the customized patterned lithographic templates containing English words, Arabic numerals, and Chinese characters are used to verify the applicability and controllability of this hybrid method. In general, our work provides a versatile strategy for the low-cost and facile preparation of hydrothermally growable metal oxide (e.g., ZnO and MnO2) nanostructures with potential applications in the fields of microelectronic devices, photoelectric devices, energy storage, and photocatalysis.

Space-Confined seeding and growth of ordered arrays of TiO2 hierarchical nanostructures.

Here, we report a facile approach to fabricate large area ordered arrays of TiO2 hierarchical nanostructures through space-confined seeding and growth on inverted pyramid templates. The mechanisms of space-confined seeding and growth have been systematically explored and studied. The drying TiO2 seed precursor solution prefers to accumulate on the narrow structures including the centre and edges of the inverted pyramid structures, which facilitates to reduce the free energy of the precursor solution surface and form crystal seeds. Followed by hydrothermal treatment, selective growth of TiO2 hierarchical nanostructures on desirable locations, such as only on the centre, only on the edges, or on the entire surface of the inverted pyramid templates, can be achieved. In addition, the growth temperature, duration and solvents affect the morphology of TiO2 hierarchical nanostructures. This work may provide a universal approach to obtain ordered arrays of metal oxide (e.g. ZnO and MnO2, etc.) nanostructures for applications in optics, electrics, energy, and catalysis.

Hybrid Lithographic Arbitrary Patterning of TiO2 Nanorod Arrays.

In this work, we report a hybrid lithographic method that combines the top-down soft lithography and the bottom-up hydrothermal approach for growing single-crystalline TiO2 nanorod arrays with arbitrary patterns. The arbitrary patterns of TiO2 seeds were obtained through the microcontact printing of the TiO2 seed precursor onto Si substrates using prepatterned poly(dimethylsiloxane) (PDMS) as stamps, followed by a baking process. Afterward, TiO2 nanorod arrays were selectively grown on patterned TiO2 seeds through conventional hydrothermal methods. By controlling the TiO2 seed precursor concentration, the hydrothermal reaction time and temperature and the patterns, the morphology and density of the TiO2 nanorods can be tuned in a controllable manner. Overall, this work provides a new strategy for the low-cost and facile preparation of patterned TiO2 nanorod arrays that has potential applications in micro-nano-optoelectronic devices and other fields.

Osteogenesis-Inducing Chemical Cues Enhance the Mechanosensitivity of Human Mesenchymal Stem Cells for Osteogenic Differentiation on a Microtopographically Patterned Surface.

Mechanical cues are widely used for regulating cell behavior because of their overarching, extensive, and non-invasive advantages. However, unlike chemical cues, mechanical cues are not efficient enough to determine cell fate independently and improving the mechanosensitivity of cells is rather challenging. In this study, the combined effect of chemical and mechanical cues on the osteogenic differentiation of human mesenchymal stem cells is examined. These results show that chemical cues such as the presence of an osteogenic medium, induce cells to secrete more collagen, and induce integrin for recruiting focal adhesion proteins that mature and cascade a series of events with the help of the mechanical force of the scaffold material. High-resolution, highly ordered hollow-micro-frustum-arrays using double-layer lithography, combined with modified methacrylate gelatin loaded with pre-defined soluble chemicals to provide both chemical and mechanical cues to cells. This approach ultimately facilitates the achievement of cellular osteodifferentiation and enhances bone repair efficiency in a model of femoral fracture in vivo in mice. Moreover, the results also reveal these pivotal roles of Integrin α2/Focal adhesion kinase/Ras homolog gene family member A/Large Tumor Suppressor 1/Yes-associated protein in human mesenchymal stem cells osteogenic differentiation both in vitro and in vivo. Overall, these results show that chemical cues enhance the microtopographical sensitivity of cells.