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Sci Adv ; 6(47)2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33208366


We demonstrate an additive manufacturing approach to produce gradient refractive index glass optics. Using direct ink writing with an active inline micromixer, we three-dimensionally print multimaterial green bodies with compositional gradients, consisting primarily of silica nanoparticles and varying concentrations of titania as the index-modifying dopant. The green bodies are then consolidated into glass and polished, resulting in optics with tailored spatial profiles of the refractive index. We show that this approach can be used to achieve a variety of conventional and unconventional optical functions in a flat glass component with no surface curvature.

ACS Appl Mater Interfaces ; 12(5): 6736-6741, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31934741


Direct ink writing (DIW) three-dimensional (3D) printing provides a revolutionary approach to fabricating components with gradients in material properties. Herein, we report a method for generating colloidal germania feedstock and germania-silica inks for the production of optical quality germania-silica (GeO2-SiO2) glasses by DIW, making available a new material composition for the development of multimaterial and functionally graded optical quality glasses and ceramics by additive manufacturing. Colloidal germania and silica particles are prepared by a base-catalyzed sol-gel method and converted to printable shear-thinning suspensions with desired viscoelastic properties for DIW. The volatile solvents are then evaporated, and the green bodies are calcined and sintered to produce transparent, crack-free glasses. Chemical and structural evolution of GeO2-SiO2 glasses is confirmed by nuclear magnetic resonance, X-ray diffraction, and Raman spectroscopy. UV-vis transmission and optical homogeneity measurements reveal comparable performance of the 3D printed GeO2-SiO2 glasses to glasses produced using conventional approaches and improved performance over 3D printed TiO2-SiO2 inks. Moreover, because GeO2-SiO2 inks are compatible with DIW technology, they offer exciting options for forming new materials with patterned compositions such as gradients in the refractive index that cannot be achieved with conventional manufacturing approaches.

Soft Matter ; 15(24): 4898-4904, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31166358


We demonstrate a scalable method to create metallic nanowire arrays and meshes over square-centimeter-areas with tunable sub-100 nm dimensions and geometries using the shear alignment of block copolymers. We use the block copolymer poly(styrene)-b-poly(2-vinyl pyridine) (PS-P2VP) since the P2VP block complexes with metal salts like Na2PtCl4, thereby enabling us to directly pattern nanoscale platinum features. We investigate what shear alignment processing parameters are necessary to attain high quality and well-ordered nanowire arrays and quantify how the block copolymer's molecular weight affects the resulting Pt nanowires' dimensions and defect densities. Through systematic studies of processing parameters and scanning transmission electron microscopy (STEM) tomography, we determine that the equivalent of 2-3 monolayers of PS-P2VP are required to produce a single layer of well-aligned nanowires. The resulting nanowires' widths and heights can be tuned between 11-27 nm and 9-50 nm, respectively, and have periodicites varying between 37 and 63 nm, depending on the choice of block copolymer molecular weight. We observe that the height-to-width ratio of the nanowires also increases with molecular weight, reaching a value of almost 2 with the largest dimensions fabricated. Furthermore, we demonstrate that an additional layer of Pt nanowires can be orthogonally aligned on top of and without disturbing an underlying layer, thereby enabling the fabrication of Pt nanowire meshes with tunable sub-100 nm dimensions and geometries over a cm2-area.

Adv Mater ; 29(26)2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28452163


Silica inks are developed, which may be 3D printed and thermally processed to produce optically transparent glass structures with sub-millimeter features in forms ranging from scaffolds to monoliths. The inks are composed of silica powder suspended in a liquid and are printed using direct ink writing. The printed structures are then dried and sintered at temperatures well below the silica melting point to form amorphous, solid, transparent glass structures. This technique enables the mold-free formation of transparent glass structures previously inaccessible using conventional glass fabrication processes.