A high throughput manufacturing process of microfluidic chips based on Roll-to-Roll imprinting is presented. With this procedure, microfluidic patterns can be produced on large area polymer substrates. The subsequent steps of inlet drilling, bonding and electrode printing are set-up on large area processes, too. Overall, this strategy allows highly parallelized processing of large numbers of chips—all costly steps of individual chip handling are avoided. The chips were used for the characterization of inorganic ions for soil nutrient analysis.

Ultrashort pulse laser systems enable new approaches of material processing and manufacturing with enhanced precision and productivity. Time- and cost-effectiveness in the context of the industrialization of ultrashort laser pulse processes require an improvement of processing speed, which is of key importance for strengthening industrial photonics based manufacturing and extending its field of applications. This article presents results on improving the speed of a laser process by parallelization for creating light deflecting volume optics. Diffractive optical elements are fabricated directly inside the encapsulant of solar modules by utilizing a spatial light modulator based parallel laser microfabrication method. The fabricated volume optical elements effectively deflect light away from front side electrodes and significantly reduce the corresponding optical losses.

The material class comprising of Cu 2 ZnSn(S,Se) 4 (CZTS) is non-toxic and comprises of abundant elements, which makes it to be very interesting for the application in solar cells. Recent progress on the understanding of the materials and devices resulted in increasing efficiencies and it is expected that these will increase further. For a commercial success of CZTS solar cells an industrial low-cost production is required. The CZTS monograin solar cell technology allows developing a solar cell production process independently from material and device research. Challenges and latest results on the roll-to-roll production of monograin CZTS solar cells are discussed and presented.

In the recent 15 years photovoltaics has become a mature technology and covers significant electricity demands in many industrialized countries. CPV still has the potential to be the most cost-competitive technology for photovoltaic power plant applications in sun-rich regions. However, the advantages of larger manufacturing scale of flat-plate modules caused troubles for CPV producers in competing with standard photovoltaic technologies. Similar is true for other alternative (or emerging) photovoltaic such as printed and flexible photovoltaic foils which can be produced at low cost in a roll-to-roll process. In this paper we present an approach to realize a flexible CPV membrane technology and investigate the technical feasibility of the approach by applying raytracing simulations and discuss potential applications of the approach. It is calculated that up to 78% of the incident sunrays can contribute to the photocurrent. On possible application of CPV membranes is found to be daylight management of buildings. In particular the membranes can be attached into or onto glazing or windows in order to improve the passive daylighting and harvest solar energy. In a second approach, the CPV membranes can be retrofitted onto existing solar-thermal collectors in order to improve their functionality without scarifying the thermal heat generation in winter time.

We show that with an appropriate combination of two optical simulation techniques—classical ray-tracing and the finite difference time domain method—an optical device containing multiple diffractive and refractive optical elements can be accurately simulated in an iterative simulation approach. We compare the simulation results with experimental measurements of the device to discuss the applicability and accuracy of our iterative simulation procedure.

In this contribution, we present two flexible thiol-ene-based hybrid materials based on epoxy and acetoxy polysiloxane matrix materials. The latter cross-linking mechanisms allow for orthogonal curing of the matrix in the presence of thiol-ene monomers enabling fast one-step access to two-photon-polymerization (2PP) curable substrates for waveguide fabrication. Another time-saving feature of our concept is the straightforward UV-flood-curing after 2PP, which is also a progress compared to previous works with elaborate postprocessing. Optimization of the ratio of thiol/ene moieties with respect to reactivity and analyses of the thermal stability of the materials, which is required for the industrial process, were carried out. Besides investigations regarding the refractive index of the materials, the proof of principle for successful waveguiding will be given. Flexible optical waveguides were successfully fabricated inside a low refractive polysiloxane matrix material.

Optical waveguides are becoming increasingly important in the developing area of broadband communications. The field of electronics is advancing rapidly, leading to further demands for larger data storage, smaller components and a better design of integrated optical circuits. The integration of optical interconnects on printed circuit boards (PCBs) requires precise technologies to make this emerging field possible. A promising new microfabrication technique, two-photon photopolymerisation (2PP) can be used to produce three dimensional structures in the sub-micron region. Near-infrared lasers can be used to create 3D optical waveguides by initiating the photopolymerisation of high refractive index monomers in polymeric matrix materials. Terminal silanol groups are intermediates for room temperature vulcaniseable (RTV) silicones and can be cross linked with functional silanes to produce flexible, transparent polymeric materials with high thermal stabilities. A silanol terminated polysiloxane; cross linked with a methyl substituted acryloxy silane has been developed as a suitable material for the fabrication of optical waveguides by two-photon absorption (TPA). A higher refractive index is achieved upon polymerisation of the acrylate functional groups. The material has been shown to be suitable in the fabrication of 3D optical waveguides with a high refractive index contrast. The cured material is fully flexible and exhibits high thermal stability and optical transparency. The material was characterised by Fourier transform infrared spectroscopy (FT-IR), simultaneous thermal analysis coupled with mass spectrometry (STA-MS) and near-infrared spectroscopy (NIRS). Waveguides were observed by phase contrast microscopy, cut back measurements and were additionally directly integrated onto specially designed PCBs by correctly positioning waveguide bundles between optoelectronic components using TPA.

There is a steadily growing demand for miniaturized bioanalytical devices allowing for on-site or point-of-care detection of biomolecules or pathogens in applications like diagnostics, food testing, or environmental monitoring. These, so called labs-on-a-chip or micro-total analysis systems (mu-TAS) should ideally enable convenient sample-in - result-out type operation. Therefore, the entire process from sample preparation, metering, reagent incubation, etc. to detection should be performed on a single disposable device (on-chip). In the early days such devices were mainly fabricated using glass or silicon substrates and adapting established fabrication technologies from the electronics and semiconductor industry. More recently, the development focuses on the use of thermoplastic polymers as they allow for low-cost high volume fabrication of disposables. One of the most promising materials for the development of plastic based lab-on-a-chip systems are cyclic olefin polymers and copolymers (COP/COC) due to their excellent optical properties (high transparency and low autofluorescence) and ease of processing.We present a bioanalytical system for whole blood samples comprising a disposable plastic chip based on TIRF (total internal reflection fluorescence) optical detection. The chips were fabricated by compression moulding of COP and microfluidic channels were structured by hot embossing. These microfluidic structures integrate several sample pretreatment steps. These are the separation of erythrocytes, metering of sample volume using passive valves, and reagent incubation for competitive bioassays. The surface of the following optical detection zone is functionalized with specific capture probes in an array format. The plastic chips comprise dedicated structures for simple and effective coupling of excitation light from low-cost laser diodes. This enables TIRF excitation of fluorescently labeled probes selectively bound to detection spots at the microchannel surface. The fluorescence of these detection arrays is imaged using a simple set-up based on a digital consumer camera. Image processing for spot detection and intensity calculation is accomplished using customized software. Using this combined TIRF excitation and imaging based detection approach allowes for effective suppression of background fluorescence from the sample, multiplexed detection in an array format, as well as internal calibration and background correction.

In this contribution we describe a microfluidic chip combining plasma separation, sample metering, dissolution/incubation with reagents stored on-chip and optical detection. The system allows defining the incubation time and works under constant externally applied pressure using only passive valves for actuation. This allowed the realization of a bioanalytical device for whole blood samples comprising a disposable plastic chip using TIRF (total internal reflection fluorescence) based optical detection of biochemical binding events.

Research into the integration of optical interconnects in printed circuit boards (PCBs) is rapidly gaining interest due to the increase in data transfer speeds now required along with the need for miniaturized devices with increased complexity and functionality. We present a method that involves embedding optoelectronic components in a polymeric material and fabricating optical waveguides in one step. A silanol-terminated polysiloxane cross-linked with an acryloxy functional silane is utilized as a matrix material into which the 3D optical waveguides are inscribed by two-photon-induced polymerization. A pulsed femtosecond laser is used to directly write optical waveguides into the material, forming an optical link between lasers and photodiodes that are directly mounted on a specially designed PCB. The boards produced were characterized by monitoring the transmitted photocurrent as well as temperature-dependent data transmission properties. Data rates exceeding 4 Gbit/s were achieved.

The lately in literature described use of two photon based photo processes for producing optical interconnections arises the need of suitable optical functional materials. The present work concerns the development, investigation and processing of a flexible siloxane based organic-inorganic hybrid (OIH) material for the fabrication of optical waveguides for data transmission on printed circuit boards (PCBs). In the developed system the waveguide core is formed by two photon induced photopolymerization (TPIP) of selected monomers, which are dissolved in a polysiloxane matrix. Through the photo induced polymerization an interpenetrating network is generated, resulting in a refractive index change between the non-illuminated waveguide cladding and the illuminated core material. Due to the optical transparency, flexibility and chemical and thermal stability, polysiloxanes were chosen as optical matrix material. Different types of methacrylates with a high refractive index were used as monomers.In order to obtain a high contrast in refractive index, the monomers were removed from non-illuminated regions in a vacuum process after laser exposure. The written optical waveguides were evidenced by phase contrast microscopy, revealing an excellent structuring behavior of the developed material. Optical techniques e.g. cut-back measurements and light extraction tests were applied to characterize the inscribed waveguide structures and to detect the resulting optical loss. Conversion rate of the monomers, which occurred through structuring, was verified by FTIR. To determine the refractive index change upon UV irradiation spectroscopic ellipsometry was applied. As a result of the polymerization, a difference of Delta n = 0.02 between the non-illuminated cladding and the illuminated core material was detected. Additionally, prototypes of optical interconnects on PCBs were fabricated by inscription of a waveguide bundle between a mounted laser and photo diode, resulting in the desired increase of the transmitted photocurrent after TPA structuring. In conclusion, the obtained results demonstrate that fully flexible optical interconnects are accessible by the developed process. (C) 2011 Elsevier B.V. All rights reserved.

Two-photon polymerization (2PP) is an emerging tool in the field of additive manufacturing technologies, which allows for the elegant 3D lithographic production by means of photosensitive resins. One key advantage of 2PP is the achievable feature resolution. A few tens of nanometers are currently the resolution limit for this novel technique. Fields of applications are as diverse as photonics, microfluidics and biomedicine. A challenging photonics application for 2PP are optical interconnects, where optical elements on printed circuit boards are connected with waveguides. The possibility for real 3D structuring allows for easier positioning of the cured structures and straightforward processing outperforming techniques such as 2D lithography or reactive ion etching in this regard. If mechanical flexibility of the printed circuit board is required as a property for certain niche applications, polysiloxanes are an interesting class of matrix material. This is also due to their low optical damping behavior and high temperature stability as the material has to withstand temperatures around 250°C during the manufacturing process. In this work, we present our latest approach to create polysiloxane-based waveguides via 2PP of specially tailored thiol-ene formulations. Latest improvements on the ease of processing and the local refractive index increase are shown as well as the proof of principle for waveguiding. Optical waveguides were successfully created via 2PP with writing speeds around 10 mm/min.

The Two-photon induced polymerization (2PP) is a novel concept in photopolymer chemistry allowing for elegant 3D direct laser writing (DLW) with resolutions down to several tens of nanometers. It has attracted significant attention in fields such as micro-electromechanical systems (MEMS), photonic crystals or surface plasmon polaritons. Additionally, 2PP can be applied for the structuring of optical waveguides by inducing a local refractive index increase over the surrounding cladding material. Herein, we present our latest work regarding high performance waveguides on the basis of polysiloxane/photopolymer hybrid materials, which we consider to be useful in the communication technology.High refractive acrylic formulations were cured via 2PP in polysiloxane films. In comparison to former works the procedure could be significantly simplified by using a thixotropic, monomer-containing polysiloxane matrix formulation, which could be UV-cured after DLW. The enrichment of monomer during the DLW process in the illuminated regions enabled us to create a refractive index increase over the surrounding material and thus eliminating the impractical evaporating of the excess monomer by simply UV-curing the whole sample after 2PP-structuring. DLW of waveguide structures was carried out using our novel two-photon initiator B3FL.

The increasing demand for miniaturization and design flexibility of polymer optical waveguides integrated into electrical printed circuit boards (PCB) calls for new coupling and integration concepts.We report on a method that allows the coupling of optical waveguides to electro-optical components as well as the integration of an entire optical link into the PCB. The electro-optical devices such as lasers and photodiodes are assembled on the PCB and then embedded in an optically transparent material. A focused femtosecond laser beam stimulates a polymerization reaction based on a two-photon absorption effect in the optical material and locally increases the refractive index of the material. In this way waveguide cores can be realized and the embedded components can be connected optically. This approach does not only allow a precise alignment of the waveguide end faces to the components but also offers a truly 3-dimensional routing capability of the waveguides.Using this technology we were able to realize butt-coupling and mirror-coupling interface solutions in several demonstrators. We were also manufacturing demonstrator boards with fully integrated driver and preamplifier chips, which show very low power consumption of down to 10 mW for about 2.5 Gbit/s. Furthermore, demonstrators with interconnects at two different optical layers were realized.

3D polymeric optical waveguides play an intrinsic role in a rapidly developing area of broadband communications. Advances in the field of electronics means there is a greater demand for higher speeds, larger data storage, smaller components and the improvement in the design of integrated optical circuits. Two-photon photopolymerisation (2PP) is a promising three-dimensional microfabrication technique, which can be used to produce structures in the sub-micron region. With the use of near-infrared (NIR) lasers, 3D optical waveguides can be fabricated in polymer-based matrix materials, based on the increase of the refractive index in the vicinity of the laser focus.The development of a new polysiloxane material, used in the study of the integration of optical interconnects on printed circuit boards is presented. The desirable properties of epoxy functional silicones crosslinked with diamines deem them suitable for such applications. An epoxy terminated polysiloxane: crosslinked with an aminopropyl disiloxane has been developed as a suitable material for the fabrication of optical waveguides by two-photon absorption (TPA). The material fulfils a number of requirements including a good refractive index contrast between the matrix material and inscribed waveguide, full flexibility and high thermal stability.The matrix material was characterised by Fourier transform infrared spectroscopy (FUR) and thermal gravimetric analysis (TGA) The optical waveguides were characterised by phase contrast microscopy, and were directly integrated onto specially designed PCB's by correctly positioning waveguide bundles between optoelectronic components using TPA, making it possible to detect transmitted photocurrents. (C) 2011 Elsevier Ltd. All rights reserved.

This paper reports how waveguides can be structured directly into a matrix made out of Poly(dimethyl siloxane) (PDMS) using 2PP.To fulfill the economical aspects of a fabrication of optical interconnects, a cost effective, mechanically flexible and temperature-resistant matrix material with a low attenuation in optical applications (smaller than 0.1 dB/cm at 850 nm wavelength) such as PDMS is needed.

The three‐dimensional fabrication of optical waveguides has gained increasing interest in recent years to establish interconnections between electrical components on a very small scale where copper circuits encounter severe limitations. In this work the application of optically clear, organically modified porous silica monoliths and thin films as a host material for polymeric waveguides to be inscribed into the solid host structure by two‐photon‐induced photopolymerization is investigated. Porosity is generated using a lyotropic liquid crystalline surfactant/solvent system as a template for the solid silica material obtained by a sol–gel transition of a liquid precursor. In order to reduce the brittleness of the purely inorganic material, organic–inorganic co‐precursor molecules that contain poly(ethylene glycol) chains are synthesized and added to the mixture, which successfully suppresses macroscopic cracking and leads to flexible thin films. The structure of the thus‐obtained porous organic–inorganic hybrid material is investigated by atomic force microscopy. It is shown that the modified material is suitable for infiltration with photocurable monomers and functional polymeric waveguides can be inscribed by selective two‐photon‐induced photopolymerization.

Organic nanoparticle dispersions are prepared via a versatile technique. Particles are formed by evaporation of aromatic hydrocarbons (like pentacene, rubrene, and tetracene) in an inert atmosphere and condensation of the vapor in a liquid medium. This allows the preparation of stable and concentrated dispersions of organic nanoparticles, showing interesting optical properties and potential applications in organic electronics and sensors.

The development of new optimized photoinitiators for the two-photon induced photopolymerization (TPIP) is essential in order to obtain high resolutions in this solid freeform fabrication process. Herein, we present the syntheses and characterizations of a series of efficient photoinitiators, comprising of a cross conjugated D-π-A-π-D system. The different donor- and acceptor functionalities of the investigated photoinitiators as well as the synthesis of targeted derivatives containing double and triple bonds in the conjugated backbone allowed the evaluation of structure-activity relationships. The basic photophysical properties as well as the activity and ideal processing window under TPIP conditions were investigated for each initiator and compared with typical commercially available one-photon initiator and with two highly potential initiators well known from literature. These tests figured out that the new chromophores are highly potential even at concentrations down to 0.05 wt%.