Embedding of optoelectrical, optical, and electrical functionalities into low-cost products like product packages and printed matter can be used to increase their information content. For these purposes, components like displays, photodetectors, light sources, solar cells, battery elements, diffractive optical elements, lightguides, electrical conductors, resistors, transistors, switching elements etc. and their integration to functional modules are required. Also the need of rapid and reliable di-agnostic systems for wellness and healthcare applications is apparent. Today the time from sampling to result can take hours or even several days. In future the target is to analyze the sample within a few minutes for further action. Additionally, the price of the components for low-end products and disposable sensors has to be in cent scale or preferably below that. Therefore, new, cost-effective, and volume scale capable manufacturing techniques are required. Recent developments of liquid-phase processable electrical and optical polymeric, inorganic, and hybrid material inks together with biocompatible materials have made it possible to fabricate functional components by conventional roll-to-roll techniques such as gravure printing on flexible paper and plastic like substrates. In this paper, we show our current achievements in the field of roll-to-roll fabricated electronics, optoelec-tronics and biosensors. With examples of light guiding structures, organic light emitting diodes, biocompatible materials etc., we demonstrate the huge potential of roll to roll fabrication as a low cost mass production technology for future low end electronic products.
Embedding of optoelectrical, optical, and electrical functionalities into low-cost products like packages and printed matter can be used to increase their information content. These functionalities make also possible the realization of new type of entertaining, impressive or guiding effects on the product packages and printed matter. For these purposes, components like displays, photodetectors, light sources, solar cells, battery elements, diffractive optical elements, lightguides, electrical conductors, resistors, transistors, switching elements etc. and their integration to functional modules are required. Additionally, the price of the components for low-end products has to be in cent scale or preferably below that. Therefore, new, cost-effective, and volume scale capable manufacturing techniques are required. Recent developments of liquid-phase processable electrical and optical polymeric, inorganic, and hybrid materials - inks - have made it possible to fabricate functional electrical, optical and optoelectrical components by conventional roll-to-roll techniques such as gravure printing, embossing, digital printing, offset, and screen printing on flexible paper and plastic like substrates. In this paper, we show our current achievements in the field of roll-to-roll fabricated, optics, electronics and optoelectronics. With few examples, we also demonstrate the printing and hot-embossing capabilities of table scale printing machines and VTT Electronic's 'PICO' roll-to-roll pilot production facility.
In this study, the sol-gel process to fabricate directly UV-photopatternable lanthanum-doped lead zirconate titanate (PLZT) films was investigated. Photosensitive films were obtained via chemical methacrylic acid modification of metal organic PLZT precursors. Spin-on deposited films were patterned using direct UV-photolithography process. Patterned films were annealed in air, in order to obtain perovskite type crystalline material. AFM and XRD techniques were used for the characterization of the material and fabricated structures. The sol-gel processed PLZT films had good crystallinity, they were crack-free, and had low surface roughness. The films exhibit electro-optic effect being therefore interesting to be used in active integrated optic devices.
We report on the fabrication of transparent, conductive and directly photopatternable, pure and Sb-doped tin dioxide thin films. Precursors used were antimony(III)isopropoxide and a photo-reactive tin alkoxide synthesized from tin(IV)isopropoxide and methacrylic acid. The synthesis of methacrylic acid modified tin alkoxide was monitored in-situ using IR- and ESI-TOF mass spectroscopic techniques. Sb-doped organo-tin films were deposited via single layer spin coating. After deposition the films were patterned via photopolymerization, using a mercury I-line UV-lamp. All investigated materials could be patterned with 3 μm features. After development in isopropanol, the films were annealed in air, in order to obtain crystalline and conductive films. The electrical conductivities of the annealed thin films with, and without, UV-irradiation were determined using a linear four-point method. The direct photopatterning process was found to increase the film conductivity for all the Sb-doping levels tested. The mechanisms for the increased conductivity were characterized using AFM, XPS and XRD techniques.
Advances in polymer and sol-gel derived hybrid materials have made possible to integrate optical structures including waveguides, sensors and structures used in passive alignment of optical devices on various type of substrates. Particular attention has been given to the fabrication of electro-optical printed circuit boards (EOPCB). Fundamental problems related to printed circuit boards (PCB) are the insufficient surface smoothness of common PCB substrate (FR4) and different coefficients of thermal expansion between the optical material and substrate. In order to resolve these problems sol-gel hybrid materials and cost effective spray-coating method are employed for the fabrication of optical structures on PCB. Surface roughness of the PCB's can be greatly reduced using additional layer under optical core material. This additional layer behaves also as an optical under-cladding layer. Optical properties of these used materials are determined and optical structures fabricated using these directly photopatternable materials are demonstrated.
This paper introduces the usage of directly UV-photopatternable sol-gel based materials and the processing methods for the fabrication of binary diffractive optical elements. We designed and modeled a binary axicon - an optical element, which produces almost diffraction free beam in a specified distance from the element. We fabricated sol-gel based hybrid-glass materials and tailored their processing parameters to fit the demands of the axicon design. Resolution of 2 microns, film thickness of 850 nm, and certain morphological properties were required. The materials were derived from zirconium(IV)isopropoxide, methacrylic acid, and methacryloxypropyltritethoxysilane. We determined the morphological and line quality of the fabricated axicons as a function of the UV-irradiation dose. In addition, we measured the optical characteristics of the axicons in terms of the axial and radial intensity profiles. The reasons for the differences between calculated and measured values are discussed.
Liquid phase deposition of sol-gel method derived hybrid glass materials is utilized for fabrication of UV light deformable thin films. The hybrid glass material undergoes a surface-relief deformation when exposed to UV light. The observed deformation phenomenon is in the form of a physical expansion of the exposed areas. The maximum deformation when the material was patterned as a sinusoidal grating was 643 nm. The hybrid glass material features an index of refraction of 1.52, rms surface roughness of 2.25 +/- 0.83 nm after processing, and extinction coefficients of 1.2 10<SUP>-3</SUP> micrometers <SUP>-1</SUP> and 0.47 10<SUP>-3</SUP> micrometers <SUP>-1</SUP> at wavelengths of 633 nm and 1550 nm, respectively.
Sol-gel processing consists several variable parameters during materials synthesis and post processing steps. The sol-gel synthesis is rather sensitive for the parameters such as pH, temperature, type of catalyst, reaction time etc. However, this sensitivity can be taken as an advantage when developing and studying new materials and their properties. Furthermore, since the sol-gel technology mainly describes the fabrication of solid state materials from a liquid phase by applying metal alkoxides or metal salts as precursors, the post processing such as sintering has critical effects on the final form and properties of the solid material. Combinatorial chemistry and methods are valuable tools to estimate the effects of different variables and to build-up combinatorial libraries for the sol-gel technique. This paper generally describes potentials and the usage motivation of combinatorial chemistry in the sol-gel technology by taking into account some major steps in the synthesis and processing which are valuable for the estimation of the final product properties. Different kind of post processing steps in the combinatorial manner are studied in details. As an example the post processing of sol-gel derived semiconductor oxides and photosensitivity of hybrid sol-gel glasses are presented. The combinatorial treatment and measurement methods for these materials are explained.
Organic polythiophene polymers are known to be good electrical conductors, however they are lacking of chemical and mechanical stability. In this paper we describe a synthesis of polyethylene dioxythiophene-polystyrene sulfonate (PEDT-PSS) doped sol-gel polyceram material to improve chemical and mechanical properties of PEDT-PSS thin films. Thin films are fabricated by spin and spray coating methods from polymer-sol-gel solutions on sodalime glass, polyurethane, polycarbonate (PC) and polymethyl methacrylate (PMMA) substrates. The effects of different kinds of silicon dioxide network forming sol-gel precursors are investigated in terms of the electrical conductivity and the stability of the electrical conducting properties against various atmospheres and chemicals. Optical transmittances at the visible wavelength region and refractive indices are also determined. Results indicate that a type and an amount of the sol-gel silane precursor have an effect on the electrical, optical and chemical properties of these films. The most conductive and stable coatings are formed when glycidyloxypropyltrimethoxysilane is used as a sol-gel precursor. The maximum conductivity obtained for 150 nm thick film is 17 S/cm. Finally some of the applications, such as antistatic protection coatings on plastics and optical thin film devices of these polycerams are described.
We are developing a silicon-based micro-optical table (MOT) on which various passive and active optical elements can be positioned with sufficient accuracy so that no further alignment is necessary. In order to achieve a zero-alignment assembly of micro-optical systems, we take advantage of lithographic patterning. Conventional lithography is used in combination with a deep reactive ion etch (DRIE) process for silicon in order to pattern a silicon substrate that plays the role of a micro-optical table. Lithography is also used to pattern optical and opto-mechanical structures on optical elements. Specifically, the hybrid sol-gel method is employed in the fabrication of optical and opto-mechanical structures into a photosensitive glass materials. High optical quality thick films and structures are fabricated by a one-step spin-coating process followed by direct UV imprinting. We have achieved a material thickness of 27.5 microns and a maximum patterned thickness of 17.4 microns at an aspect ratio of 0.6. The material exhibits a minimum transmittance of 97 percent between 400-1100 nm, an index of refraction of 1.49, and an rms surface of 14.8 roughness of 14.8 nm after development.
In this paper we present the results of the first fabrication and micro-assembly experiments of a silicon- wafer based micro-optical table (MOT). Based on these experiments, estimates of position accuracy are reported. We also report on progress in fabrication of lens elements in a hybrid sol-gel material (HSGM). Diffractive optical elements have been patterned in a 13-micron thick HSGM layer on a 150-micron thick soda-lime glass substrate. The measured rms surface roughness was 20 nm. Finally, we describe modeling of MOT systems using non-sequential ray tracing.
Antimony doped tin dioxide (SnO<SUB>2</SUB>:Sb) thin films are fabricated by a new simplified sol-gel process. Films are prepared from an alcoholic solution of SnCl<SUB>4</SUB>(DOT)4H<SUB>2</SUB>O doped with SbCl<SUB>3</SUB>. Films are deposited by the spin coating process on sodalime glass, borosilicate glass, silicon wafers and ceramic alumina substrates. The chemical reactions during the heat treatment are monitored by DSC and TG. The chemical composition of the coatings are determined by scanning electron microscopy (SEM). Sheet resistance, R<SUB>s</SUB>, is measured using a linear four-probe technique. Optical properties of the films are also determined. The resistivity of the thin films are presented as a function of the antimony doping level. The smallest sheet resistance of 200 (Omega) /$DAL is found for a 250 nm thick coating on a borosilicate substrate. It is observed that the sheet resistance does not decrease linearly with increasing film thickness. Fabrication possibilities of these materials for the integrated optics based sensors including patterning methods are discussed.