Optical capillaries are used in gas and liquid chromatography, electrophoresis, absorbance spectroscopy, Raman spectroscopy, etc. The use of optical capillaries in these micro-fluidic techniques emerged in the 1990s and generated new applications in biotechnologies, medical diagnostic, drug discovery and environmental sciences. The wide range of possible capillary constructions allows them to be tailored advantageously to specific applications. In the present work we discuss some aspects of integration of the photonic heads that use optical capillaries in micro-fluidic systems. The field of research is multidisciplinary, comprising certain aspects of physics of micro fluid sample motion, optical detection and the adaptation of the technology to practical applications. To make it possible to analyze small volumes of fluids, we analyzed the light guidance in capillary tubing. We examined both theoretically and experimentally the phenomena of light propagation, under various conditions, in optical capillaries partially filled with a liquid. We have shown that the light propagation depends on the construction of the capillary, its length and the position of the inserted drop of liquid. We designed and constructed structures built of silicon substrates and thin wall capillaries, and then examined theoretically and experimentally how, on heating the capillary locally, the vapor phase of the micro liquid sample forms in the structures. The results obtained show that, using small liquid samples with volumes below 10 −8 cm 3 , the micro-fluidic systems equipped with capillary tubing can be used as the sensors of the surface tension, viscosity, boiling point and vapor pressure of the liquid and its heat capacity. The proposed system provides information that allows determination of the type of the liquid especially when the data are analyzed using neural networks.

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