Fully Integrated Microfluidic Device with Carbon Sensing Electrode

We have developed a fully integrated capillary electrophoresis (CE)-based microfluidic device with an integrated carbon sensing electrode. A combination of microfabrication protocols were employed for fabricating the hybrid PDMS/glass microfluidic device including chemical wet etching, soft lithography, and micromolding techniques. The microdevice is comprised of a glass substrate with integrated gold electrodes, a carbon sensing electrode, and a polydimethyl siloxane (PDMS) slab that encompasses the microchannel network. The carbon sensing electrode was physically characterized via atomic force microscopy (AFM) and Raman spectrometry. In addition, its quality was evaluated electrochemically and compared to commercial glassy carbon electrodes upon performance of cyclic voltammetric analysis of two illicit drugs, morphine and codeine. The analytical performance of the stand-alone microdevice was evaluated upon testing the injection, separation, and amperometric detection on the carbon sensing electrode. The carbon sensing electrode provides a stable background current during the application of a high sensing potential, which is necessary for sensing molecules that can only be detected at high potentials such as morphine and codeine.