Poly(3,4-ethylenedioxythiophene)-Modified Electrodes for Microfluidics Pumping with Redox-Magnetohydrodynamics:...

A new approach using electrodes modified with poly(3,4-ethylenedioxythiophene) (PEDOT) was implemented to perform redox-magnetohydrodynamics (MHD) microfluidics and eliminate the need to add redox species to solution, thus removing interferences with detection, sample, and reagents for lab-on-a-chip applications. This accomplishment not only retains the unique properties of redox-MHD pumping (i.e., programmable fluid speeds and flow patterns without the need for side walls, horizontal flat flow profiles, looping flow, no electrode corrosion, and no bubble formation), but also achieves a wider sustainable voltage range and currents that can be as much as 7+ times higher (and therefore correspondingly higher velocities) than in past studies involving unmodified electrodes and redox species in solution. PEDOT, a conducting polymer that has been shown to exhibit low cytotoxicity, was electropolymerized on microband gold electrodes (25 mm long ×103 μm wide). A cell (325 μL) with distant side walls was formed by placing a 620 μm thick poly(dimethylsiloxane), PDMS, gasket with an opening of 3.2 cm × 1.5 cm on the chip, and a glass slide lid prevented evaporation. A 0.37 T magnet under the chip generated a magnetic field perpendicular to the chip surface. The cell was filled with 0.095 M NaCl electrolyte containing 10 μm polystyrene beads to visualize and quantify fluid flow using optical video microscopy. Fluid speeds of 590 μm s(-1) were observed immediately after applying a potential step. A linear relationship between applied electronic current and fluid velocity was shown. Vertical flow profiles under applied current conditions were curved, with a weak parabolic fit.