Electrical Control of Debye Screening in Liquid Microchannels for Ionic Separations

In this work we demonstrate controlled electrostatic depletion and accumulation of liquid ions in microscale channels by applying voltage across a dielectric coating on the channel walls. A 100 muM fluorescent ionic dye (FITC) was flown through a series of oxidized (SiO₂) Si microscale channels (each 10 mum wide, 15 mum deep and 1cm long). Negative and positive voltages on the Si substrate were used to deplete and accumulate the negative fluorescent FITC2" ions, respectively. Theoretically calculated plots were used confirm the experimental results. This ability to screen ionic species based on charge can now be applied towards creating a platform for multidimensional separations (charge, surface energy, size) in a single lab-on-chip format.