In this study, the design, realization and measurement results of a novel optofluidic system capable of performing absorbance-based flow cytometric analysis is presented. This miniaturized laboratory platform, fabricated using SU-8 on a silicon substrate, comprises integrated polymer-based waveguides for light guiding and a biconcave cylindrical lens for incident light focusing. The optical structures are detached from the microfluidic sample channel resulting in a significant increase in optical sensitivity. This allows the application of standard solidstate laser and standard silicon-based photodiodes operated by lock-in-amplification resulting in a highly practical and effective detection system. The easy-to-fabricate singlelayer microfluidic structure enables independently adjustable 3D hydrodynamic sample focusing to an arbitrary position in the channel. To confirm the fluid dynamics and raytracing simulations and to characterize the system, different sets of microparticles and T-lymphocyte cells (Jurkat cell line) for vital staining were investigated by detecting the extinction (axial light loss) signal. The analytical classification via signal peak height/width demonstrates the high sensitivity and sample discrimination capability of this compact low-cost/low-power microflow cytometer.

Novel optical techniques for sensitive and reproducible fluorescence single cell analysis utilizing setups without single photon counting units are attractive for enhanced low-cost cell parameter screening. In this contribution we present the first microfluidic planar device to form an optofluidic adjustable convex lens with three-dimensional light focusing ability to improve optical sensor systems.

Flow cytometry is a standard analytical method in cell biology and clinical diagnostics and is widely distributed for the experimental investigation of microparticle characteristics. In this work, the design, realization, and measurement results of a novel planar optofluidic flow cytometric device with an integrated three-dimensional (3D) adjustable optofluidic lens system for forward-scattering∕extinction-based biochemical analysis fabricated by silicon micromachining are presented. To our knowledge, this is the first planar cytometric system with the ability to focus light three-dimensionally on cells∕particles by the application of fluidic lenses. The single layer microfluidic platform enables versatile 3D hydrodynamic sample focusing to an arbitrary position in the channel and incorporates integrated fiber grooves for the insertion of glass fibers. To confirm the fluid dynamics and raytracing simulations and to characterize the sensor, different cell lines and sets of microparticles were investigated by detecting the extinction (axial light loss) signal, demonstrating the high sensitivity and sample discrimination capability of this analysis system. The unique features of this planar microdevice enable new biotechnological analysis techniques due to the highly increased sensitivity.

In this paper we present the design and operation of a micro flow cell comprising a liquid-core/liquid-twin-cladding waveguide for on-chip fluorescence spectroscopy based on evanescent field illumination. The application of an inner (sample) and outer cladding stream minimizes the sample volume for optical measurements and ensures the analyte position in the evanescent field for excitation at the core/cladding interface. The fiber-chip-coupled laser light is guided by the fluidic waveguide providing a uniform excitation along the analysis channel. Fluorescence intensity measurements of different sample solutions were conducted to illustrate the operational quality. The fluidics device is fabricated by laser microstereolithography in 1.5 h.

We present a microfluidic chip for fluorescent single particle measurement, featuring three-dimensional hydrodynamic focusing and an integrated self-aligned microlens which has an adjustable focal area. Microlenses are a powerful option to increase particle detection sensitivity but generally they are limited to one focal point. The newly developed self-aligned microlens with adjustable refractive index allows focusing the stimulating laser beam for different sample fluids and hence combines increased sensitivity with versatility of the optical measurement method. The three-dimensional hydrodynamic focusing provides a stream of seriatim particles in the channel, which is an important precondition for single particle measurement. With this design, fabricated in SU-8, single fluorescent particle measurement was successfully carried out.