A high-density nanowire electrode on paper for biomedical applications

Paper-based devices have heralded a new direction for low-cost, point-of-care medical diagnostics. In this paper, we bring the benefits of nanotechnology to paper-based diagnostics by presenting a room temperature, low-cost process to fabricate high-density nanowires directly on paper substrates using template-assisted electrodeposition and simple adhesive tape-based patterning. Different types of nanowires made from platinum, nickel and copper are fabricated and patterned with microscale resolution on paper substrates. Nanowires are characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and impedance spectroscopy. The approach was used to make dry paper-based nanowire electrodes that exhibit excellent electrode-tissue impedance suitable for recording electrocardiogram signals without any wet-gel adhesives. Another application employed a nanowire electrode on paper as a cathode in batteries for energy harvesting from natural acidic sources. The battery generated sufficient power of around 6 mW with dimensions of just 4 cm2 from a simulated gastric acid environment. Many more applications ranging from high surface area electrodes for supercapacitors and batteries to next generation chemical and biological sensors will be enabled by the proposed approach of bringing nanotechnology to paper-based devices.