Abstract We characterize shapes and volumes of droplets generated in PDMS T-junctions and assess the use of this type of microfluidic device to generate droplets suitable for the study of… Click to show full abstract
Abstract We characterize shapes and volumes of droplets generated in PDMS T-junctions and assess the use of this type of microfluidic device to generate droplets suitable for the study of nucleation. Water droplets were formed in oil in a PDMS T-junction and subsequently stored. Droplet volume reproducibility and stability were investigated from acquired micrographs. By theoretically analyzing the influence of the mean volume of a population of droplets on the estimation of nucleation rates, we have shown that deviations in mean volumes can seriously affect the estimates, unless such deviation is smaller than 10%. This condition is fulfilled if experiments are repeated using the same microdevice. Measured droplet polydispersity remained low enough to treat the droplets as monodisperse. Immersing the microdevice in a water bath mitigates solvent evaporation, and allows for very accurate temperature control. Finally, a screening procedure was used to select the ideal operating conditions to obtain droplets with the desired sizes. Applying this method in devices with increasing T-junction cross sectional area, we have demonstrated a scaling-up of droplet volumes close to an order of magnitude while tuning the droplet shape, i.e., the average length to width ratio, at values between 1 and 1.2.
               
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