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Superposition of successive frames illustrating drop switching by local thermocapillary actuation the arrow indicates the laser location observed by the fluorescence of the water-dye solution. (a) , , , , frame rate 50 frames/s. (b) , , . , frame rate 100 frames/s. (c) , , . , frame rate 100 frames/s. Flow rates are expressed in .
Drop velocity in the and directions (defined in left inset) with (filled symbols) and without (empty symbols) of laser actuation for , , , . The main slowing down in the direction is due to the enlargement of the Y junction. Left inset: trajectory of the drop center of mass for various beam powers for the same flow rates (from bottom to top: , 48, 53, ). The beam location is indicated by the dot at (, ). Right Inset: Variation of the mean drop velocity induced by the laser beam for the nine couples of flow rates used.
Switching efficiency vs the ratio of the mean drop velocity in the and directions for the nine flow rate couples investigated (symbols are the same as in Fig. 2). Inset: switching efficiency plotted vs .
Sorting of pure water and water/dye droplets by local thermocapillary actuation. Top picture: superposition of 200frames showing three drops which are naturally drawn toward the lower outlet without laser. Bottom set: decomposition of the superposition of 209 frames when the laser shines droplets; the arrow indicates the laser location. Switching only occurs for water/dye ones ( and where a pure water drop closely follows a water/dye one). , , and , frame rate .
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