Development and Performance Evaluation of Stretchable Silver Pastes for Screen Printing on Thermoplastic Polyurethane Films

Efficient, stretchable wiring electrodes are achieved when the resistance change during expansion and contraction is minimal. Herein, we prepared silver pastes specifically designed for screen printing on thermoplastic polyurethane films; they exhibit minimal resistance changes. The pastes were prepared using silver particles with sizes of 2 and 7 mu m as well as a mixture of 2 and 7 mu m silver particles (50:50 wt%). These pastes were analyzed using methods such as rheological measurements, thermogravimetric analysis, printability tests, tensile and torsion tests, and light-emitting diode (LED) tests. The most promising results were obtained when exclusively using 2 mu m silver flake particles. The pastes demonstrated a viscosity of 24,880 cps, a thixotropic index value of 2.82, excellent printability, and consistent resistance measurements even after 100% stretch, thus indicating exceptional tensile properties. Moreover, the pastes exhibited substantial stability, with no change in brightness after the attachment of seven LEDs at 20% tension.