@article{min_zhang_chang_2016, title={Designing unit cell in three-dimensional periodic nanostructures using colloidal lithography}, volume={24}, ISSN={["1094-4087"]}, DOI={10.1364/oe.24.00a276}, abstractNote={Colloidal phase-shift lithography, the illumination of a two-dimensional (2D) ordered array of self-assembled colloidal nanospheres, is an effective method for the fabrication of periodic three-dimensional (3D) nanostructures. In this work, we investigate the design and control of the unit-cell geometry by examining the relative ratio of the illumination wavelength and colloidal nanosphere diameter. Using analytical and finite-difference time-domain (FDTD) modeling, we examine the effect of the wavelength-diameter ratio on intensity pattern, lattice constants, and unit-cell geometry. These models were validated by experimental fabrication for various combination of wavelength and colloid diameter. The developed models and fabrication tools can facilitate the design and engineering of 3D periodic nanostructure for photonic crystals, volumetric electrodes, and porous materials.}, number={2}, journal={OPTICS EXPRESS}, author={Min, Joong-Hee and Zhang, Xu A. and Chang, Chih-Hao}, year={2016}, month={Jan}, pages={A276–A284} }
 @article{elek_zhang_dai_xu_chang_2015, title={Fabrication of three-dimensional hierarchical nanostructures using template-directed colloidal assembly}, volume={7}, ISSN={["2040-3372"]}, DOI={10.1039/c4nr06840h}, abstractNote={Optical effects in template-directed colloidal assembly are explored to fabricate microscale patterns with integrated three-dimensional (3D) nanostructures.}, number={10}, journal={NANOSCALE}, author={Elek, J. E. and Zhang, X. A. and Dai, B. and Xu, Z. and Chang, C. -H.}, year={2015}, pages={4406–4410} }
 @article{bagal_dandley_zhao_zhang_oldham_parsons_chang_2015, title={Multifunctional nano-accordion structures for stretchable transparent conductors}, volume={2}, ISSN={["2051-6355"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000359586600003&KeyUID=WOS:000359586600003}, DOI={10.1039/c5mh00070j}, abstractNote={Nano-accordion structures allow brittle materials to stretch, enabling transparent conductors that are stretchable and flexible.}, number={5}, journal={MATERIALS HORIZONS}, author={Bagal, Abhijeet and Dandley, Erinn C. and Zhao, Junjie and Zhang, Xu A. and Oldham, Christopher J. and Parsons, Gregory N. and Chang, Chih-Hao}, year={2015}, month={Sep}, pages={486–494} }
 @article{zhang_bagal_dandley_zhao_oldham_wu_parsons_chang_2015, title={Ordered 3D Thin-Shell Nanolattice Materials with Near-Unity Refractive Indices}, volume={25}, ISSN={["1616-3028"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000365532100009&KeyUID=WOS:000365532100009}, DOI={10.1002/adfm.201502854}, abstractNote={The refractive indices of naturally occurring materials are limited, and there exists an index gap between indices of air and available solid materials. With many photonics and electronics applications, there has been considerable effort in creating artificial materials with optical and dielectric properties similar to air while simultaneously being mechanically stable to bear load. Here, a class of ordered nanolattice materials consisting of periodic thin‐shell structures with near‐unity refractive index and high stiffness is demonstrated. Using a combination of 3D nanolithography and atomic layer deposition, these ordered nanostructured materials have reduced optical scattering and improved mechanical stability compared to existing randomly porous materials. Using ZnO and Al2O3 as the building materials, refractive indices from 1.3 down to 1.025 are achieved. The experimental data can be accurately described by Maxwell Garnett effective media theory, which can provide a guide for index design. The demonstrated low‐index, low‐scattering, and high‐stiffness materials can serve as high‐quality optical films in multilayer photonic structures, waveguides, resonators, and ultra‐low‐k dielectrics.}, number={42}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Zhang, Xu A. and Bagal, Abhijeet and Dandley, Erinn C. and Zhao, Junjie and Oldham, Christopher J. and Wu, Bae-Ian and Parsons, Gregory N. and Chang, Chih-Hao}, year={2015}, month={Nov}, pages={6644–6649} }
 @article{zhang_dai_xu_chang_2015, title={Sculpting Asymmetric, Hollow-Core, Three-Dimensional Nanostructures Using Colloidal Particles}, volume={11}, ISSN={["1613-6829"]}, DOI={10.1002/smll.201402750}, abstractNote={Colloidal elements have historically played a key role in “bottom‐up” self‐assembly processes for nanofabrication. However, these elementary components can also interact with light to generate complex intensity distributions and facilitate “top‐down” lithography. Here, a nanolithography technique is demonstrated based on oblique illuminations of colloidal particles to fabricate hollow‐core 3D nanostructures with complex symmetry. The light–particle interaction generates an angular light distribution as governed by Mie scattering, which can be compounded by multiple illuminations to sculpt novel 3D structures in the underlying photoresist. The fabricated geometry can be controlled by the particle parameters and illumination configurations, enabling the fabrication of a large variety of asymmetric hollow nanostructures. The proposed technique has high pattern versatility, is low cost and high throughput, and can find potential application in nanoneedles, nanonozzles, and materials with anisotropic properties.}, number={11}, journal={SMALL}, author={Zhang, Xu A. and Dai, Bin and Xu, Zhiyuan and Chang, Chih-Hao}, year={2015}, month={Mar}, pages={1285–1292} }
 @article{zhang_elek_chang_2013, title={Three-Dimensional Nanolithography Using Light Scattering from Colloidal Particles}, volume={7}, ISSN={["1936-086X"]}, DOI={10.1021/nn402637a}, abstractNote={The interaction between light and colloidal elements can result in a wealth of interesting near-field optical patterns. By examining the optical and colloidal properties, the intensity distribution can be tailored and harnessed for three-dimensional nanolithography. Here, we examine the use of light scattering from colloidal particles to fabricate complex hollow nanostructures. In this approach, a single colloidal sphere is illuminated to create a scattering pattern, which is captured by a photoresist in close proximity. No external optical elements are required, and the colloidal elements alone provide the modulation of the optical intensity pattern. The fabricated nanostructures can be designed to have multiple shells, confined volumes, and single top openings, resembling "nano-volcanoes." The geometry of such structures is dependent on the scattered light distribution and can be accurately modeled by examining the light-particle interaction. The hollow nanostructures can be used to trap nanomaterial, and we demonstrate their ability to trap 50 nm silica nanoparticles. These well-defined surface hollow structures can be further functionalized for applications in controlled drug delivery and biotrapping. Colloidal elements with different geometries and material compositions can also be incorporated to examine other light-colloid interactions.}, number={7}, journal={ACS NANO}, author={Zhang, Xu A. and Elek, Jonathan and Chang, Chih-Hao}, year={2013}, month={Jul}, pages={6212–6218} }