Recent theoretical predictions indicate that a shift in surfactant transport mechanism from diffusion controlled to kinetically controlled occurs at highly curved interfaces where the length scale is on the same order as feature sizes in microfluidic devices. At present, experimental evidence of this shift in transport mechanism is lacking and this is due to the limitations on degree of interface curvature imposed by traditional methods of surface tension measurement. We show that the measurement of dynamic surface tension is possible at highly curved interfaces using a microfluidic tensiometer that utilizes glass micropipettes to control curvature dimension. Comparison of dynamic surface tension data from our microfluidic tensiometer with data obtained from traditional techniques will validate the theoretical arguments reported, and will improve understanding of two phase flows in microfluidic devices.

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