Figure (B) shows an optical micrograph plan view of the assembled system containing a chip, and three microfluidic channels in the correct orientation with the inlets and outlets for sample flow over the sensors. Tubes are omitted for clarity. A silicon chip device consisting of three sensors and on-chip counter and reference electrodes is shown in Figure (A) (Supp info) while S1 (B) (Supp info) shows an assembled microfluidic system, with the inlet and outlet tubes removed for clarity. Typically, inlet and outlet tubes would be connected to allow flow through the selected microchannel over a selected sensor. The distal ends contact pads of a microchip were connected to an external SD connector port, as shown. This allowed facile connection to an Autolab potentiostat.