Flexible Microgap Electrodes by Direct Inkjet Printing for Biosensing Application

A rapid fabrication method of microgap electrodes using inkjet printing is described. In this approach, the lateral spacing between two printed electrode lines is precisely controlled down to 1 µm without any surface modification or substrate patterning. The strong confinement, well below typical resolution of inkjet printing, relies on complete solvent evaporation between the printing of adjacent electrode structures, which is achieved by controlling the printing speed and temperature profiles. The feasibility of this method is demonstrated by writing electrode structures with two distinct inks, based on carbon and silver nanoparticles, with comparable results. As an application proof-of-principle, arrays of microgap electrodes are fabricated using a carbon nanoparticle ink for electrochemical detection based on redox-cycling, a technique in which the sensitivity of the device depends on the distance between the two electrodes. The redox-cycling amplification of electrochemical signals is demonstrated and it is shown that the printed microgap device can be used as an electrochemical biosensor for the determination of human immunodeficiency virus (HIV)-related single-stranded DNA. This work presents a promising new approach for fabricating low-cost and label-free redox-cycling biosensors using all-inkjet-printed electrodes.