Nozzle design for the generation of plane liquid surfaces

Measurements besides total fluorescence intensity of more elaborate optical techniques such as light scattering, extinction as well as fluorescence polarization and slit scan profiles have been reported in various cell sorter design studies. However the cylindrical liquid stream in air, common to many research system, limits the optical properties of the system. We report the successful application of three new types of nozzles, all having in common the fact that the main optical axes intersect plane liquid surfaces. This has been achieved on the basis of a double sheath arrangement, which we have reported previously. The nozzles generate fluid streams with either rectangular, square or triangular cross-sections at the location of the optical axis. The latter facilitates the alignment of two beams with different wavelengths on the same optical axis within the liquid. Square or rectangular cross-sections improve light scattering and extinction measurements and may well be better suited to more complicated geometrical analysis of cells and particles in flow streams.