We demonstrate the feasibility of organic semiconductor lasers as light sources for lab-on-a-chip systems. These lasers
are based on a 1D- or 2D-photonic crystal resonator structure providing optical feedback in the active laser material that
is deposited on top, e.g. aluminum tris(8-hydroxyquinoline) (Alq3) doped with the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM). We investigated different fabrication methods for the resonator
structures, like thermal nanoimprint, UV nanoimprint, and laser interference lithography. Different substrate materials
commonly used in lab-on-a-chip systems, e.g. PMMA, Topas, and Ormocer were deployed. By changing the distributed
feedback grating periodicity, we demonstrate a tuning range for a single material system of more than 120 nm.
The investigated organic semiconductor lasers are optically pumped. External optical pumping provides a feasible
way for one-time-use chips. Our recent success of pumping organic lasers with a low-cost laser diode also renders hand-held
systems possible.
As a further step towards the integration of organic lasers in sensor systems, we demonstrate the coupling of an
organic laser into polymeric waveguides which can be combined with microfluidic channels. The integrated organic
lasers and the waveguides are both fabricated on the same polished PMMA substrate using thermal nanoimprint
lithography and deep-UV modification, respectively. We could demonstrate the guiding of the laser light in single-mode
waveguides.
This paper describes the development of methods for the determination of the characteristics and the behavior of living
neural cells. A technology which is used is the deep ultraviolet (DUV) modification of methylmethacrylate polymers
which leads to a new surface chemistry affecting the selective absorption of proteins and the adhesion of living cells in
vitro. The bi-functionality of the modified polymer chips supporting waveguides and cell anchorage capabilities at the
same time provides the opportunity to monitor protein adsorption, cell attachment and spreading processes by
evanescent-field techniques. This allows the defined spatial control of a cell/surface interaction and leads to a
combination of desired biological and optical properties of the polymer. Among them are the high sensitivity of cultured
mammalian cells to, for example, environmental changes and special features of integrated optical waveguides like their
online compatibility, minuteness and robustness. The scientific fields, biology and optics, meet at the polymer surface
becoming a cell culture substrate together with an optical waveguide by the application of special patterning and
fabrication technologies. In addition to the already mentioned fabrication and immobilization technology, the technique
proposed also offers the possibility of being able to couple to microstamping processes and to also incorporate electrical
measurements on individual cells. Thus, by extending this method and coupling it to the DUV technique described above
the possibility is given of being able to simultaneously optically and electrically interrogate individual cellular processes
with spatial resolution.
The use of conventional fabrication techniques for the fabrication of polymer based photonic integrated waveguide circuits is a necessary step to reduce costs. The replication of rib waveguides is presented using nickel shims. Results of replicated waveguides and 1 x 2 multimode interference (MMI) couplers are shown.
Deep UV-induced modification of the refractive index of polymers is a useful technique for low cost realization of
integrated optical circuits for telecommunication und sensor applications. The combination with replication techniques
like injection molding and hot embossing give the capability of a monolithic integration of these waveguide structures in
optical or fluidic microsystems. In addition the hybrid integration of these integrated optofluidic microsystems with
organic or inorganic photodiodes will open up the possibility to development novel, cheap, disposable integrated optical
sensors for environmental, chemical and biological monitoring.
We investigate the deep-UV-induced refractive index modification of alicyclic methacrylate copolymers for realizing integrated optical circuits for the development of cheap, disposable integrated optical sensors for chemical and biological monitoring. These novel copolymers obtain higher glass transition temperature (Tg), refractive index and lower water absorption than conventional poly(methylmethacrylate) (PMMA). At the same time, the adhesion of living mammalian cells on the UV exposed polymer surface was investigated for the application for biosensor.
Polymer optical waveguide devices will play a key role in several rapidly developing areas such as optical networks, biophotonic and fluidic applications. We have developed a technology which enables the increase of the refractive index of methylmethacrylate based polymers by deep ultra violet (DUV) radiation. The modification of the dielectric properties of polymers by DUV is a useful technique for the realization of photonic integrated optical circuits. The
technique presented here has several advantages with respect to common methods because only a single polymer layer is used, which serves as the substrate and waveguide as well and no further etching or development step is required. This method can not only be applied to planar polymer substrates but also to preembossed substrates. This enables the fabrication of ridge waveguide based devices by hot embossing. Nickel stampers with feature heights of about 15-20 μm and aspect ratios usually between 2:1 and 3:1 can be utilized for replication without major effort. Nickel stampers are not only used to replicate optical waveguides, but are also used to realize fluidic channels in the range of several microns. UV modification of methylmethacrylate polymers additionally leads to a new surface chemistry affecting the selective absorption of proteins and the adhesion of living cells in vitro. The bi-functionality of the modified polymer chips supporting waveguides and cell anchorage capabilities at the same time provides the opportunity to monitor protein adsorption, cell attachment and spreading processes by evanescent-field techniques.
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