Inkjet printing was conducted by a common Canon inkjet printer (IP4500 series) with a 20 µm spacing. The patterns were designed by a 2003 MS Office sofeware. Ink was printed on a standard Si/SiO2 substrate with gold electrodes (5mm sqrs). Sensor's electrical characterization was conducted using a CHI LSV method from -0.1 to 1.0 V with a step of 0.02V to determine the ohmic resistances.