Abstract
A Y-channel design is proposed to find the zeta potential for PDMS and PDMS/glass microchannels with the current monitoring technique. The major advantages of this design are four fold: i) the displacement process can be quickly repeated many times increasing the amount of measurements for a single fluid; ii) start and end times are well defined since there is minimal diffusion at the liquid/liquid interface; iii) overall preparation and operation are simplified; and iv) errors caused by undesirable pressure driven flow (Laplace and head differences) and changes in pH due to electrolysis are suppressed. The zeta potential found from current monitoring experiments with the new Y-channel design gave similar results when compared to results found in literature using a conventional straight channel design. Modifications on the slope calculation method were proposed and results agreed with the total length calculation method within 6.8% variation of the zeta potential values averaged for all experiments compared to the total length method. Using the new design, the zeta potential of a number of commonly used buffer solutions for protein and DNA application were tested in PDMS and PDMS/glass hybrid channels.