Another article describes a novel electrochemical three-electrode system integrated on nitrocellulose membrane (NC) using magnetron sputtering technology for the detection of Cu2+ and other heavy metal ions. The paper-based sensor chip exhibited a uniform arrangement of porous structure without further film modification, which allowed for an increased effective working area of the electrode. The integrated sensor showed good linearity for Cu2+ detection within the ranges of 5-200 μg•L-1 and 200-1000 μg•L-1 with a limit of detection of 2 μg•L-1. In addition, the paper-based sensor chip was capable of detecting other heavy metal ions such as Zn2+, Cd2+, Pb2+ and Bi3+ with good linearity.