Redox cycling effect at microchannel-integrated sandwich electrodes consisting of a suspended mesh and a substrate-bound planar electrode

Electrochemical sensing based on redox cycling is widely used as the detection scheme in microfluidic devices because of its simple configuration and relatively high sensitivity. However, integrating dual microelectrodes to enable redox cycling in the microchannel requires complex and cumbersome alignment procedures. In this paper, we present a simple alignment-less fabrication method for microchannel-integrated sandwich electrodes consisting of a suspended carbon mesh electrode and a substrate-bound planar electrode. Because the long carbon posts that support the suspended mesh serve as microchannel side walls, simple oxygen-plasma-assisted bonding of a flat polydimethylsiloxane plate can complete channel integration. Despite the cavity of the suspended mesh, the proposed electrochemical sensing platform exhibits a good redox cycling efficiency that is comparable to twin-plate electrodes because of the small cavity size. We also demonstrate the advantages of channel integration in redox cycling with respect to the sensitivity and selectivity in dopamine sensing.