Student Integration of microfluidic and photonic components within transparent cyclic olefin copolymers by using fs laserTuesday (23.06.2020) 11:50 - 12:10 Room 1
Lab-on-a-chip systems are based on components to transport, mix, separate and analyze small volumes of various fluids. The consecutive integration of exceedingly complex functions into a single and compact chip demands for multilayer systems. As the classical production, using a stacking and joining of single processed layers, is elaborate and limited in terms of multilayer structures, an uprising trend to fabricate those devices is the internal, three-dimensional processing of transparent substrates by using femtosecond laser pulses.
In this study, we report on the integration of microfluidic channels and optical components by focusing femtosecond laser radiation inside transparent cyclic olefin copolymer (COC) bulk material. Based on nonlinear absorption of high intensities inside the focal volume, an internal localized material modification is triggered. Size and shape of the three-dimensional internal modification are controlled by using an adaptive beam shaping setup as depicted in Fig. 1 (a). The irradiated areas show a positive refractive index shift and can be used as Type I internal optical waveguides. Furthermore, a precise control of the spatial pulse-to-pulse distance in combination with a suitable beam profile enables the integration of functional photonic elements e.g. Bragg gratings into the waveguide, which can be used for sensing applications. In addition to that, internal fs laser induced modifications are characterized by a lower thermal stability as compared to the pristine polymer material. By performing a post-annealing process step of the polymer sample, internal hollow microstructures are created by a gaseous degradation of the exposed areas. Circular microchannels with a cross sectional diameter below 100 µm can be generated in a freely chosen layout by employing motorized 3D stages. By avoiding the use of etchants, the studied technology enables the creation of internal microfluidic architectures with theoretically unlimited channel length, as there is no restriction arising from an etching selectivity. This contribution paves the way towards the fabrication of internal three-dimensional optofluidic devices created by femtosecond laser direct writing inside of transparent polymers.
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