Cost-effective stretchable Ag nanoparticles electrodes fabrication by screen printing for wearable strain sensors

To apply strain sensor as wearable and stretchable electronics, we fabricated cost-effective and stretchable Ag nanoparticle (NP) electrodes on polyurethane (PU) by using simple screen printing. By wavy and horseshoe-type patterning of the Ag NP electrode as a function of line width, we fabricated the stretchable electrodes simply, with low sheet resistances of 1.64-2.85 Ohm/square at room temperature. The screen-printed Ag NP electrodes with 3-mm line width showed a constant resistance change until the strain of 20% (wavy pattern) and 15% (horseshoe pattern). The stretchability of 15-20% is relatively small compared with other stretchable materials. Considering inorganic Ag NP electrodes, the stretchability of 15-20% is fairly high and acceptable in fabrication of stretchable electronics. In addition, a very small critical inner and outer bending radius below 1 mm indicates that the screen-printed Ag NP electrodes could also be used as highly flexible electrodes. A possible stretching mechanism was suggested to understand the good flexibility and stretchability of screen-printed Ag NP electrodes on PU substrate. Furthermore, we applied screen-printed Ag NP electrodes as stretchable interconnects for light-emitting diodes and as stretchable electrodes for strain sensors. Successful detection of human motion by wearable strain sensors indicates the potential of Ag NP electrodes as a stretchable electrode for wearable and stretchable sensors.