Sébastien Méance

A multicolor microfluidic droplet dye laser with single mode emission

A digital microfluidic dye laser that integrates a Fabry–Perot cavity with two fiber-based mirrors is shown to exhibit a single mode emission. In addition, fast switching is achieved via the alternation of droplet streams that contain two different dyes. Single-longitudinal-mode emission is observed for each dye wavelength (at 565 and 586 nm) with a linewidth narrower than 0.12 nm. This system appears thus well suited for on-chip spectroscopy and flow cytometry.

Electrochemiluminescence on-a-chip: Towards a hand-held electrically powered optofluidic source

We report a microfluidic platform that integrates several parallel optical sources based on electrochemiluminescence (ECL) of 9,10-diphenylanthracene (DPA) as luminophore agent. The annihilation of DPA radicals provides a low wavelength emission at λ=430 nm in the blue-visible range. By varying the distance between electrodes for each ECL integrated source, this glass/PDMS/glass platform enabled a systematic investigation of the main electrochemical parameters involved in ECL. These parameters have been studied either in a static mode or in a dynamic one. Even at slow flow rate (~2 µl s(-1)), the renewal of electroactive species could be easily promoted inside the microfluidic channel which gives rise to a stable optical intensity for several minutes. Compared with traditional optically pumped dye sources, this microfluidic system demonstrates that ECL can be easily implemented on chip for producing much compact optofluidic sources. Such simply electrically powered system-on-chip would surely encourage the future of hand-held µTAS devices with integrated fast detection and embedded electronics.

Study of Surface Charge Instabilities by EOF Measurements on a Chip: A Real-Time Hysteresis and Peptide Adsorption Based Methodology

This paper describes the measurement of the electroosmotic mobility (EOF) in a Wheatstone fluidic bridge (μFWB) as a direct probe of the surface instability. The variation of EOF known as one major contribution of the electrokinetic migration has been determined with a real-time measurement platform after different conditionings on chips. We also scan the pH of the background electrolytes with three different ionic strengths to evaluate the dependencies of the EOF as a function of the pH. A hysteresis methodology has been developed for probing the surface charge instabilities. EOF mobility has been recorded during on-a-chip electrophoresis to estimate the effect of such instability on the analytical performance. As expected, our experimental curves show that a decrease in the ionic strength increases the surface charge stability of the hybrid microchip. This result demonstrates that ionic exchanges between the surface and the fluid are clearly involved in the stability of the surface charge. With this original method based on real-time EOF measurement, the surface state can be characterized after hydrodynamic and electrophoresis sequences to mimic any liquid conditioning and separation steps. Finally, as a demonstrative application, isotherms of the adsorption of insulin have been recorded showing the change in surface charge by unspecific adsorption of this biomolecule onto the microfluidic channels wall. These methodologies and findings could be particularly relevant to investigating various analytical pathways and to understanding the molecular mechanisms at solid/liquid interfaces.

Laser intracavity analysis of droplets by multicolour microfluidic dye laser

An original method based on a microfluidic dye laser has been investigated to carry out optical analysis of microfluidic droplets. Droplets that have been the subject of extensive works over the last five years appear as the best tool to manipulate subnanoliter volumes for a lot of applications in both chemistry and biology. We have designed a device that combines a microfluidic dye laser and a droplet generator on the same chip. Intracavity measurement can thus be performed as the droplets pass through the laser cavity. Depending on the droplet shape, whether it is spherical or not, the presence of the droplet inside the optical cavity results in an extinction of the laser signal or in a variation of its intensity. This innovative method can be used for in-situ direct analysis of any event occuring inside the droplet volume. In addition to this work, in order to develop a device allowing optical analysis over the full visible spectrum, we have also developed a new laser that is able to deliver multiple wavelength on-demands. Such improvement in the laser design has several advantages such as reducing the number of equipment around the set-up.