Fluid flows in “T” or “Y” shaped structures of microchannels are studied in order to develop modeling approaches as well as adapted measurement techniques. The applications of these structures are numerous and concern in particular biology and chemical engineering for which the integration of microchannels in lab-on-chip and/or microreactor is an important challenge. Our works concern the development of a measurement technique for the study of the filling of a “T” shaped microchannel structure by a liquid. In the studied channels, the experimental constraints are strong. Indeed, the space steps involved within the phenomena are very much reduced and vary from 1 to 10 μm. Moreover, the dynamics of the flow implies a high acquisition frequency, ranging from 10 to 100 Hz. Our technological choice is based on the measurement of the attenuation of an X-ray beam in the matter. The main advantage of this non-intrusive technique is that it can be implemented even in media opaque to visible light. Also, that X-ray techniques can theoretically reach a better space resolution than optical ones. The measurement technique is quantitative and a 3D measurement is achievable by tomography. These methods are validated for problems located at centimetric space steps and high acquisition frequencies, [1], [2]. The objective of this work is to match the microfluidics field requirement (space steps and attenuation contrast), while preserving high time frequencies. Our experimental bench consists of a X-ray generator, that makes possible to obtain high enlargements of the observed object whit a reduced blur in the image. The image is obtained by a pixel detector called Medipix2. This detector is under development within a European collaboration which gathers 16 partners around the CERN, the CEA being a partner. The main assets of this detector are its high space resolution, its operational photon counting mode and its high acquisition frequency. The presented works constitute a very first implementation and validation of the proposed technique for the microfluidics field. Experimental results are obtained and presented. They allow a measurement of the filling conditions of the “T” shape structure of microchannels. The orientations and research perspectives to improve the obtained results by the technique could be evaluated accurately and important basis of our work are now established and quantified for the future.
Characterization of the PILATUS photon-counting pixel detector for X-ray energies from 1.75 keV to 60 keV
