Fabrication of micro‐ and nanostructures at line‐speed of 60 m min−1 by large‐area roll‐to‐roll extrusion coating is demonstrated. Nanopillars with diameters 80 nm and heights 100 nm are replicated in polypropylene. The main limiting factor for replication on nanoscale is the retardation time for solidification of the melt.
Well‐defined nano‐topographies were prepared by electron‐beam lithography and electroplated to form nickel‐shims. The surface pattern consisted of square pillars repeated equidistantly within the plane of the surface in a perpendicular arrangement. The width and distance between the squares both ranged from 310 to 3100 nm. All the pillars were 220 nm high. The nickel‐shim was used as a surface‐template during injection molding of polycarbonate. Secondly, a nickel shim, with a surface pattern consisted of a squared sine with a period of 700 nm and amplitude of 450 nm, was mounted on, and it was in good thermal contact with the upper plate in a hot‐press. Polycarbonate/polystyrene was melted on the lower plate while the temperature of the shim was kept below the glass transition temperature. The upper plate was lowered until the shim was in contact with the melt. Experiments were carried out with a clean shim and a shim coated with a monolayer of fluorocarbonsilane. As a result of the surface coating, the amplitude of the replicated grating decreased from about 350 nm in polycarbonate and 100 nm in polystyrene to less than 10 nm. The experiments strongly suggest that the possibility to injection mold sub‐micrometer surface structures in polymers mainly relates to adhesive energy between polymer and shim. POLYM. ENG. SCI. 46:160–171, 2006. © 2005 Society of Plastics Engineers
Lab-scale plasmonic color printing using nano-structured and subsequently metallized surfaces have been demonstrated to provide vivid colors. However, upscaling these structures for large area manufacturing is extremely challenging due to the requirement of nanometer precision of metal thickness. In this study, we have investigated a plasmonic color meta-surface design that can be easily upscaled. We have demonstrated the feasibility of fabrication of these plasmonic color surfaces by a high-speed roll-to-roll method, comprising roll-to-roll extrusion coating at 10 m min creating a polymer foil having 100 nm deep pits of varying sub-wavelength diameter and pitch length. Subsequently this polymer foil was metallized and coated also by high-speed roll-to-roll methods. The perceived colors have high tolerance towards the thickness of the metal layer, when this thickness exceeds the depths of the pits, which enables the robust high-speed fabrication. This finding can pave the way for plasmonic meta-surfaces to be implemented in a broader range of applications such as printing, memory, surface enhanced Raman scattering (SERS), biosensors, flexible displays, photovoltaics, security, and product branding.
We demonstrate the use of roll-to-roll extrusion coating (R2R-EC) for fabrication of nanopatterned polypropylene (PP) foils with strong antiwetting properties. The antiwetting nanopattern is originated from textured surfaces fabricated on silicon wafers by a single-step method of reactive ion etching with different processing gas flow rates. We provide a systematic study of the wetting properties for the fabricated surfaces and show that a controlled texture stretching effect in the R2R-EC process is instrumental to yield the superhydrophobic surfaces with water contact angles approaching 160° and droplet roll-off angles below 10°.
Microinterferometric backscatter detection (MIBD) has previously been shown capable of measuring changes in the refractive index of liquids on the order of 10(-7). The MIBD technique is based on interference of laser light after it is reflected from different regions in a capillary. These reflections generate an interference pattern that moves upon changing refractive index of the liquid in the capillary. The small-angle interference pattern traditionally considered has a repetition frequency in the refractive index space that limits the ability to measure refractive index-to-refractive index changes causing such a repetition. Such refractive index changes are typically on the order of three decades. Recent modeling and experiments with the MIBD technique have shown that other intensity variations in the pattern are present for larger backscattered angles. By considering these variations, we have shown two methods by which it is possible to extend the dynamic measurement range to make an absolute refractive index measurement. One method utilizes variations in the Fresnel coefficients while the second approach is based on the refractive index-dependent onset of total internal reflection angles. With the second approach, we have been able to measure the absolute refractive index of a liquid with a precision of 2.5 x 10(-4).
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