Magnetic-field-assisted assembly of metal/polymer/metal junction sensors

We present a method to assemble Au/polyaniline/Au junctions and demonstrate a chemical sensor application. The building blocks consist of an array of microelectrodes on a silicon chip, microfabricated metallic bars, and a thin polyaniline layer deposited on the microelectrodes or on the bars. The individual bars suspended in solution are placed, with the help of a magnetic field, across the microelectrodes to form the junctions. The polyaniline layer is ∼30 nm thick and modified with glycine-glycine-histidine oligopeptides. Strong binding of ${\mathrm{Cu}}^{\text{2+}}$ to the oligopeptide is converted into a conductance change of the junctions, allowing selective detection of trace amounts of ${\mathrm{Cu}}^{\text{+2}}$ ions.