Immobilization of Active Antibodies at Polymer Melt Surfaces during Injection Molding.

We demonstrate the transfer and immobilization of active antibodies from a low surface- energy mold surface to thermoplastic replica surfaces using injection molding, and we investigate the process at molecular scale. The transfer process is highly efficient, as verified by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) of the mold and replica surfaces. AFM analysis reveals partial nanometer-scale embedding of the protein into the polymer matrix as a possible mechanism of permanent immobilization. Replicas with rabbit anti-mouse IgG immobilized as capture antibody at the hot polymer melt surface during injection molding show similar affinity for their antigen (mouse IgG) in sandwich enzyme-linked immunosorbent assay (ELISA) as capture antibodies deposited by passive adsorption onto a bare thermoplastic replica. The transferred antibodies retain their functionality after incubation in serum-containing cell medium for >1 week. A mold coating time of 10 min prior to injection molding is sufficient for producing highly sensitive ELISA assays, thus enabling the short processing cycle times required for mass production of single-use biodevices relying on active immobilized antibodies.

Plasmonic color metasurfaces fabricated by a high speed roll-to-roll method.

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-1 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.

Superhydrophobic Properties of Nanotextured Polypropylene Foils Fabricated by Roll-to-Roll Extrusion Coating.

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°.

Absolute refractive index determination by microinterferometric backscatter detection.

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).