Title: Curvature-Adjustable Polymeric Nanolens Fabrication Using UV-Controlled Nanoimprint Lithography
Nanolenses are gaining importance in nanotechnology, but their challenging fabrication is thwarting their wider adoption. Of particular challenge is facile control of the lens’ curvature. In this work, we demonstrate a new nanoimprinting technique capable of realizing polymeric nanolenses in which the nanolens’ curvature is optically controlled by the ultraviolet (UV) dose at the pre-curing step. Our results reveal a regime in which the nanolens’ height changes linearly with the UV dose. Computational modeling further uncovers that the polymer undergoes highly nonlinear dynamics during the UV-controlled nanoimprinting process. Both the technique and the process model will greatly advance nanoscale science and manufacturing technology. more »« less
Ji, Myung Gi; Sikder, Rabiul Islam; Kim, Jaeyoun
(, SPIE)
Piyawattanametha, Wibool; Park, Yong-Hwa; Zappe, Hans
(Ed.)
Understanding the dynamic behavior of photopolymers in nanoscale environment is essential to improving MEMS/NEMS device fabrication technologies. Here, we unveil the highly nonlinear behaviors of photopolymers exhibited during the process of light-controlled, low-pressure nanoimprinting. Such peculiarities can complicate the relation between the UV-dose and the height of the nanoimprinted feature, degrading the accuracy of the height control. To address the issue, we establish a theoretical process model and used the control of the nanoimprinting height for structural coloring applications. Our findings will broadly benefit nanotechnology and nanoscience.
Guo, L. Jay
(, The 62th International Conference on Electron, Ion, and Photon Beam Technology and Nanofabrication)
Nanoimprinting has been applied in many micro- and nanoscale engineered devices; applications include displays, organic electronics, photovoltaics, optical films, and optoelectronics; and in some cases, direct imprinting of functional polymeric devices. Applications in the photonics area can significantly relieve the stringent requirement needed for nanoelectronics. We provide examples of structural colors and optical meta-surfaces facilitated by nanoimprinting, as well as plasmonic lithography masks that can produce deep-subwavelength structures using ordinary UV light. Inkjet printing has been widely used in many applications, but still faces challenges in pattern precision and feature variations. Combining Nanoimprint for patterning and inkjet printing for material deposition will take the advantage of what both technologies can offer, and can provide a high precision additive manufacturing process. We will show printed photonic devices, e.g. electro-optic polymer based optical modulators. To extend nanoimprinting to solid materials other than polymeric films will require innovative and non-conventional approaches. One such process is Metal-assisted chemical (Mac) imprint, which combines MacEtch and nanoiprint and enables direct MacEtch of Si substrate using a hybrid imprinting mold having noble metal mask. However, only low aspect ratio structures have been obtained because of the mass-transport limitation in the previous molds. Recently we effectively solved this problem by a using a specially made mold of Pt-coated anodized aluminum oxide (AAO) membrane, where the holes through the entire thickness drastically enhances the mass-transport. As a result, very high aspect ratio Si nanowires were achieved by MacImprint.
Sikder, Rabiul Islam; Ji, Myung Gi; Kim, Jaeyoun
(, SPIE)
Piyawattanametha, Wibool; Park, Yong-Hwa; Zappe, Hans
(Ed.)
Recently, there have been notable advances in nanophotonic structural color generation which enabled various applications in display, anti-counterfeiting, sensors and detectors. However, most advances in this domain have been achieved through the use of high-index materials which require expensive and complex fabrication. In this work, we enable low-index polymer nanostructures to generate structural colors using the multipolar decomposition technique which allows a better understanding and design of the scattering process by identifying the dominant multipole modes from the scattered fields. We set a polymeric (n~1.56) cuboid as the structural color generation platform, examined the contributions of various multipoles from the wave scattered by it, and synthesized the desired color spectrum by adjusting only the height of the cuboid. To validate our findings, we fabricated the designed structural color pixels via light-controlled, low-pressure nanoimprinting and measured the color and spectrum from them. Our experimental results agreed well with the simulation results, providing insights for bringing further advances to structural coloring.
Freeman, Sebastian; Kibler, Karen; Lipsky, Zachary; Jin, Sha; German, Guy K.; Ye, Kaiming
(, Scientific Reports)
Abstract The ongoing COVID-19 global pandemic has necessitated evaluating various disinfection technologies for reducing viral transmission in public settings. Ultraviolet (UV) radiation can inactivate pathogens and viruses but more insight is needed into the performance of different UV wavelengths and their applications. We observed greater than a 3-log reduction of SARS-CoV-2 infectivity with a dose of 12.5 mJ/cm 2 of 254 nm UV light when the viruses were suspended in PBS, while a dose of 25 mJ/cm 2 was necessary to achieve a similar reduction when they were in an EMEM culture medium containing 2%(v/v) FBS, highlighting the critical effect of media in which the virus is suspended, given that SARS-CoV-2 is always aerosolized when airborne or deposited on a surface. It was found that SARS-CoV-2 susceptibility (a measure of the effectiveness of the UV light) in a buffer such as PBS was 4.4-fold greater than that in a cell culture medium. Furthermore, we discovered the attenuation of UVC disinfection by amino acids, vitamins, and niacinamide, highlighting the importance of determining UVC dosages under a condition close to aerosols that wrap the viruses. We developed a disinfection model to determine the effect of the environment on UVC effectiveness with three different wavelengths, 222 nm, 254 nm, and 265 nm. An inverse correlation between the liquid absorbance and the viral susceptibility was observed. We found that 222 nm light was most effective at reducing viral infectivity in low absorbing liquids such as PBS, whereas 265 nm light was most effective in high absorbing liquids such as cell culture medium. Viral susceptibility was further decreased in N95 masks with 222 nm light being the most effective. The safety of 222 nm was also studied. We detected changes to the mechanical properties of the stratum corneum of human skins when the 222 nm accumulative exposure exceeded 50 J/cm 2 .The findings highlight the need to evaluate each UV for a given application, as well as limiting the dose to the lowest dose necessary to avoid unnecessary exposure to the public.
Hardison, Anna L.; Talukdar, Tahmid H.; Kravchenko, Ivan I.; Ryckman, Judson D.
(, Conference on Lasers and Electro-Optics, Technical Digest Series)
We report the fabrication of gradient index flat optics and waveguides using the ‘nanoimprinting refractive index’ (NIRI) technique applied to mesoporous silicon substrates. Optical wavefront shaping and waveguiding are demonstrated in the visible and near-infrared respectively.
Li, Qiang, Ji, Myung, Chapagain, Ashish, Cho, In, and Kim, Jaeyoun. Curvature-Adjustable Polymeric Nanolens Fabrication Using UV-Controlled Nanoimprint Lithography. Retrieved from https://par.nsf.gov/biblio/10438813. Micromachines 13.12 Web. doi:10.3390/mi13122183.
Li, Qiang, Ji, Myung, Chapagain, Ashish, Cho, In, and Kim, Jaeyoun.
"Curvature-Adjustable Polymeric Nanolens Fabrication Using UV-Controlled Nanoimprint Lithography". Micromachines 13 (12). Country unknown/Code not available. https://doi.org/10.3390/mi13122183.https://par.nsf.gov/biblio/10438813.
@article{osti_10438813,
place = {Country unknown/Code not available},
title = {Curvature-Adjustable Polymeric Nanolens Fabrication Using UV-Controlled Nanoimprint Lithography},
url = {https://par.nsf.gov/biblio/10438813},
DOI = {10.3390/mi13122183},
abstractNote = {Nanolenses are gaining importance in nanotechnology, but their challenging fabrication is thwarting their wider adoption. Of particular challenge is facile control of the lens’ curvature. In this work, we demonstrate a new nanoimprinting technique capable of realizing polymeric nanolenses in which the nanolens’ curvature is optically controlled by the ultraviolet (UV) dose at the pre-curing step. Our results reveal a regime in which the nanolens’ height changes linearly with the UV dose. Computational modeling further uncovers that the polymer undergoes highly nonlinear dynamics during the UV-controlled nanoimprinting process. Both the technique and the process model will greatly advance nanoscale science and manufacturing technology.},
journal = {Micromachines},
volume = {13},
number = {12},
author = {Li, Qiang and Ji, Myung and Chapagain, Ashish and Cho, In and Kim, Jaeyoun},
}
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