Microstructured light guiding plate for single-sided light emission as light source for room illumination.

Microstructured light guiding plates (LGP) open up new capabilities in the design of energy efficient and flexible light sources for room lighting. One desirable application is the illumination of office rooms by LGPs located mainly at the façade. Starting with the requirements of an ideal light distribution curve for uniform room lighting, suitable optical microstructures have been designed and investigated by numerical ray tracing methods to be integrated in façade elements. The maximum of the desired light distribution curve for the test case is at an angle of 96° with respect to the vertical direction. The designed micro-system meets this requirement very well at an angle of 98° and a light cone width of 25°. The light emission of the proposed LGP is highly efficient with 80% coupling efficiency.

Configurable low-cost plotter device for fabrication of multi-color sub-cellular scale microarrays.

The construction and operation of a low-cost plotter for fabrication of microarrays for multiplexed single-cell analyses is reported. The printing head consists of polymeric pyramidal pens mounted on a rotation stage installed on an aluminium frame. This construction enables printing of microarrays onto glass substrates mounted on a tilt stage, controlled by a Lab-View operated user interface. The plotter can be assembled by typical academic workshops from components of less than 15,000 Euro. The functionality of the instrument is demonstrated by printing DNA microarrays on the area of 0.5 cm2 using up to three different oligonucleotides. Typical feature sizes are 5 µm diameter with a pitch of 15 µm, leading to densities of up to 10(4)-10(5) spots/mm2. The fabricated DNA microarrays are used to produce sub-cellular scale arrays of bioactive epidermal growth factor peptides by means of DNA-directed immobilization. The suitability of these biochips for cell biological studies is demonstrated by specific recruitment, concentration, and activation of EGF receptors within the plasma membrane of adherent living cells. This work illustrates that the presented plotter gives access to bio-functionalized arrays usable for fundamental research in cell biology, such as the manipulation of signal pathways in living cells at subcellular resolution.

Microoptics for efficient redirection of sunlight.

Ray-tracing calculations are employed to identify basic design rules for the configuration of microstructured daylighting systems. The results show the advantage of combinations of lenslike geometries in comparison to conventional microprism arrays regarding the overall light redirection efficiency as well as the producibility and cost efficiency. Measurements at silicone prototypes and large scale industrially produced acrylic panels confirmed the simulation results. Optimization leads to free-form geometries which can further be improved by selective roughening of specific microsurfaces.

High fidelity neuronal networks formed by plasma masking with a bilayer membrane: analysis of neurodegenerative and neuroprotective processes.

Spatially defined neuronal networks have great potential to be used in a wide spectrum of neurobiology assays. We present an original technique for the precise and reproducible formation of neuronal networks. A PDMS membrane comprising through-holes aligned with interconnecting microchannels was used during oxygen plasma etching to dry mask a protein rejecting poly(ethylene glycol) (PEG) adlayer. Patterns were faithfully replicated to produce an oxidized interconnected array pattern which supported protein adsorption. Differentiated human SH-SY5Y neuron-like cells adhered to the array nodes with the micron-scale interconnecting tracks guiding neurite outgrowth to produce neuronal connections and establish a network. A 2.0 µm track width was optimal for high-level network formation and node compliance. These spatially standardized neuronal networks were used to analyse the dynamics of acrylamide-induced neurite degeneration and the protective effects of co-treatment with calpeptin or brain derived neurotrophic factor (BDNF).

Design for reliability of polysiloxane-based electrical-optical circuit boards.

Based on the standards for optical components in telecommunications (Telcordia) and general printed circuit boards (Institute of Printed Circuits and International Electro Technical Commission), three environmental stability verification tests are concluded for polysiloxane-based electrical-optical circuit boards (EOCBs). In terms of defined test models, the respective acceleration factors are determined. Combining the acceleration factors and proposed reliability objective of 400 failures in time (FITs) (one FIT is equal to one device failure in 10(9) device hours of operation) at the 90% confidence level, EOCB test sample size to each acceleration test are deduced, and a corresponding amount of samples are prepared for mechanical and optical stabilities verification. In addition to the good mechanical stability the results exhibit, the packaged EOCBs have low and stable optical loss values (<0.1 dB/cm) and numerical aperture even at extreme environmental conditions. Furthermore, a total failure rate of 400 FITs is predicted for 14.4 yr of operation at 25 degrees C and moderate humidity conditions (20% relative humidity).

Addressable microfluidic polymer chip for DNA-directed immobilization of oligonucleotide-tagged compounds.

A microfluidic polymer chip for the self-assembly of DNA conjugates through DNA-directed immobilization is developed. The chip is fabricated from two parts, one of which contains a microfluidic channel produced from poly(dimethylsiloxane) (PDMS) by replica-casting technique using a mold prepared by photolithographic techniques. The microfluidic part is sealed by covalent bonding with a chemically activated glass slide containing a DNA oligonucleotide microarray. The dimension of the PDMS-glass microfluidic chip is equivalent to standard microscope slides (76 x 26 mm(2)). The DNA microarray surface inside the microfluidic channels is configured through conventional spotting, and the resulting DNA patches can be conveniently addressed with compounds containing complementary DNA tags. To demonstrate the utility of the addressable surface within the microfluidic channel, DNA-directed immobilization (DDI) of DNA-modified gold nanoparticles (AuNPs) and DNA-conjugates of the enzymes glucose oxidase (GOx) and horseradish peroxidase (HRP) are carried out. DDI of AuNPs is used to demonstrate site selectivity and reversibility of the surface-modification process. In the case of the DNA-enzyme conjugates, the patterned assembly of the two enzymes allows the establishment and investigation of the coupled reaction of GOx and HRP, with particular emphasis on surface coverage and lateral flow rates. The results demonstrate that this addressable chip is well suited for the generation of fluidically coupled multi-enzyme microreactors.

A new two-chip concept for continuous measurements on PMMA-microchips.

A new concept for continuous measurements on microchips is presented. A PMMA (polymethylmethacrylate) based capillary electrophoresis chip with integrated conductivity detection is combined with a second chip, which undertakes the task of fluid handling and electrical connections. The combination of electrokinetic and hydrodynamic flows allows long-term continuous stable analyses with good reproducibilities of migration time and peak heights of analytes. The two-chip system is characterized in terms of stability and reproducibility of separation and detection of small ions. Relative standard deviations of <1% and 3% respectively for retention times and peak heights during long-term measurements can be achieved. The new system combines simple handling and automated analysis without the need for refilling, cleaning or removal of the separation chip after one or several measurements.