In this work, three-dimensional ͑3D͒ SU-8 micro-and nanostructures were fabricated using a reversal UV imprint process at low temperature and low pressure. The SU-8 polymer was coated on a patterned glass mold and then transferred onto various substrates by reversal UV imprint at a typical temperature of 50°C, pressure of 1 MPa, and UV exposure of 1 s. The lower temperature and pressure used compared to conventional thermal imprint shorten the imprint time and alleviate pattern distortion. A combination of silanes was used to generate a medium surface energy on the imprint molds to enable polymer spin coating and mold release after imprint. In addition, an O 2 plasma was used for glass mold treatment to improve uniformity of silane coating and to increase substrate surface energy for better polymer adhesion. Using this technology, 100 nm-1 m wide SU-8 gratings were fabricated on flat or patterned substrates with good fidelity. By repeating this process, multiple-level nanochannels, cavities, or air-bridging polymer structures with 400 nm-10 m widths have been demonstrated. The surface energy of SU-8 was modified using an O 2 plasma to promote layer adhesion for 3D stacking. This reversal UV imprint technology offers versatility and flexibility to stack polymer layers and multiple-level sealed fluidic channels.
Resonance Raman spectra of bilirubins IX alpha, III alpha, and XIII alpha and mesobilirubin XIII alpha in alkaline aqueous and chloroform solutions are reported. Partial band assignments of bilirubin IX alpha are proposed. The model compounds confirm assignments of bands of the Raman spectrum of bilirubin IX alpha to each of the two different pyrromethenones. Resonance Raman spectra of mesobilirubin IV alpha, vinylneoxanthobilirubinic acid, and vinylisoneoxanthobilirubinic acid in alkaline aqueous solution and of the tetra-n-butylammonium salt of bilirubin IX alpha are used to define markers for the presence or absence of internal hydrogen bonds. Interaction of bilirubin dianion and sphingomyelin liposomes is studied. The Raman evidence suggests that in the bilirubin dianion/liposome complex the intramolecular hydrogen bonds between the propionate groups and the lactam NH/CO are ruptured. It is proposed that in the complex the bilirubin propionates form ion pairs with the quaternary ammonium ion of the choline moiety of sphingomyelin.
A holographic notch filter with a 15-nm rejection band is used as a Rayleigh line filter for Raman spectroscopy with a single-stage grating spectrograph. The filter is shown to allow acquisition of Stokes and anti-Stokes spectra as close as 72 cm−1 from the exciting line.
Articles you may be interested inLarge-diameter roll mold fabrication method using a small-diameter quartz roll mold and UV nanoimprint lithography J. Vac. Sci. Technol. B 29, 06FC08 (2011); 10.1116/1.3657524 Evaluation of fluorine additive effect on cationic UV-nanoimprint resin J. Vac. Sci. Technol. B 29, 06FC04 (2011); 10.1116/1.3653513Easy duplication of stamps using UV-cured fluoro-silsesquioxane for nanoimprint lithography There is a wide range of applications for three-dimensional ͑3D͒ nanochannels in biomedical systems and fluidic control. In this article, a simple and versatile technique to create 3D nanochannels with width from 200 nm to 2 m is demonstrated using sequentially stacked reversal UV nanoimprint of SU-8. Its advantages include controllable channel profile, low pressure and temperature for imprints, and flexibility in designing 3D channels by stacking. In a typical reversal UV imprint, SU-8 is spin coated on a glass mold and then transferred onto Si substrates by an UV imprint process at low temperature of 55°C, low pressure of 2 MPa, and UV exposure of 1 -4 s. While reversal UV imprinting top SU-8 layer onto bottom SU-8 layer, the UV exposure and imprint sequence of the top SU-8 layer and its effect on channel profile control are investigated. It has been found that initially UV-cured top SU-8 layer is preferred for good channel profile control because UV-cured SU-8 layer is prevented from flowing down into bottom SU-8 layer.
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