Using nanoparticles as direct-injection printing ink to fabricate conductive silver features on a transparent flexible PET substrate at room temperature

Conductive metallic features that are flexible could have application in integrated circuits, ranging from large-area electronics to low-end applications. This paper shows the creation of conductive silver thin film and wire on the transparent flexible polyethylene terephthalate (PET) substrate by a room-temperature chemical reduction process. One-step synthesis and spectroscopic characterizations of size-controlled silver nanoparticles are also described. Transmission electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric-mass analysis, X-ray photoelectron spectroscopy and synchrotron radiation X-ray diffraction were used to characterize the dodecanoate-protected silver nanoparticles. Silver metal film and wire were produced by soaking the dodecanoate-protected silver nanoparticle film and wire, which were prepared, respectively, by spin-coating and by directly drawing with a commercial Epson T50 inkjet printer onto the flexible PET substrate using Ag nanoparticles suspended in cyclohexane (10 wt.%) as the ink, in an aqueous solution containing 80% N₂H₄. The resistivities of the Ag films are actually lower compared with the Ag thin films prepared by other conventional chemical routes, such as using silver salts as metallo-organic precursors. It is suggested that the use of nanoparticles as a precursor may be an explanation for the lower resistivity.