Low-Cost and Disposable Electrowetting-on-Dielectric Lab on a Chip With an Integrated Electrochemical Detector Fabricated by Screen-Printing Process

In this paper, a low-cost and disposable electrowetting-on-dielectric (EWOD) digital microfluidic chip with an integrated electrochemical detector was fabricated based on a screen printing process. T-junction EWOD electrodes for merging buffer and analyte droplets were formed by screen-printing of silver paste before covering with spin-coated polydimethylsiloxane dielectric and Teflon AF hydrophobic layers, respectively. The electrochemical detector comprising three electrodes, including carbon working, carbon counter, and silver/silver chloride reference electrodes, was subsequently deposited on the dielectric layer by two additional screen-printing steps. The system was tested for rapid electrochemical analyses of nicotinamide adenine dinucleotide and L-ascorbic acid. The analyte and buffer droplets were blended under the EWOD actuation with varying concentrations and detected at the electrochemical detector using cyclic voltammetry. The results showed good detection performances with medium sensitivity, moderate detection limits, and short total analysis times of less than 14 s. Therefore, the screen-printed EWOD chip with integrated screen-printed carbon electrodes could be a promising alternative for low-cost automated chemical analyses.