A DNA/RNA detection technology is provided. The open flow detection technique includes a substrate defining a pair of opposing microchannels, a pair of opposing electrodes in the opposing microchannels, and at least one ion exchanging nanomembrane coupled between the opposing microchannels such that the opposing microchannels are connected to each other only through the nanomembrane, wherein the nanomembrane is functionalized with a probe complementary to the macromolecule. A voltammeter is provided to measure the electrical current or potential across the nanomembrane, and detect a change in the measured electrical current or potential to quantify the presence of the macromolecule.