Natalie Stutzmann

Patterning of polymer-supported metal films by microcutting

The ability to micropattern materials is of great importance for manufacturing advanced electronic, optical and mechanical devices ranging from displays to biosensors. For this purpose a variety of methods have been developed, including X-ray, electron-beam and photo-lithography, microcontact printing, embossing, micromoulding and cold welding. But these techniques are often of restricted applicability, involve a multitude of elaborate and cumbersome processing steps, or require aggressive chemistry. Here we describe a simple and versatile way to create well resolved metallic structures on polymer substrates, which is based on solid-state embossing of metal-coated polymer films. Ductility of both the metal layer and the polymer substrate permits the metal to be cut into surprisingly regular, micrometre-size structures. We illustrate the method by preparing patterned electrically conducting structures, highly efficient infrared polarizers and polarization-dependent colour filters.

Solid-state replication of relief structures in semicrystalline polymers

The feasibility of structuring the surfaces of semicryst. polymers is explored using poly(tetrafluoroethylene-co-hexafluoropropylene) as a model material. Hot embossing was performed in the polymer melt at 330 Deg after which the samples were quenched at room temp. [on SciFinder (R)]

Microcutting Materials on Polymer Substrates

The production of micrometer and sub-micrometer features over large areas for use in electronic and optical structures remains challenging, particularly as requirements extend beyond traditional electronic materials to ceramics and polymers. We demonstrate that the technique of microcutting allows patterning of such structures on polymer substrates of these materials as exemplified by the ceramic indium tin oxide (ITO) and the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT). Given the brittleness of most ceramics such as ITO, this is very unexpected, but we find no evidence for microcracking and find high electrical conductivities in narrow tracks (∼2.5 μm) that are separated by less than 500 nm. The micrometer-scale patterns also act as very efficient alignment layers for liquid crystals (LCs), and allow complex alignment patterns.

Novel Polarized-Light Emitting Polymer Systems

A novel, polymer bilayer illumination system is presented from which linearly polarized light is emitted. Separation of the two polarization directions is achieved by total internal reflection of the undesired light component at the polymer-polymer interface. Model systems comprising optically isotropic polystyrene (PS) sheets and oriented, birefringent poly(ethylene terephthalate) (PET) films with a relief structure to direct the light out of the systems displayed high polarizing capabilities: contrast ratios of over 10 for viewing angles between -10° and +20° were recorded in case of uncollimated incoming light. The use of a collimated light source resulted in contrast ratios of 20 up to over 40 over a viewing angle regime of -20° to +15°.

Novel polarized-light emitting polymer systems: II. Use of form birefringent polarization-selective mirrors

In reflectivity measurements on submicron-embossed polystyrene films, we found that form-birefringent polymer gratings can be described by generalized Fresnel equations for a biaxially anisotropic film in an optically isotropic medium. Thus, polarized-light emitting illumination systems may be envisioned that basically consist of an optically isotropic substrate, into which light is coupled from an external light source, and a second layer, which comprises a form-birefringent, submicron relief structure on the bottom surface that acts as polarization-selective mirror and a light out-coupling structure on the top surface. Such a design should simplify device manufacturing considerably as the main parts of the systems could be produced by injection molding using inexpensive bulk polymers.