Abstract
Printing functional devices on flexible substrates requires printing of high conductivity metallic patterns. To prevent deformation and damage of the polymeric substrate, the processing (printing) and post-processing (annealing) temperature of the metal patterns must be lower than the glass transition temperature of the substrate. Here, a hybrid process including deposition of a sacrificial blanket thin film, followed by room environment nozzle-based electrodeposition, and subsequent etching of the blanket film is demonstrated to print pure and nanocrystalline metallic (Ni and Cu) patterns on flexible substrates (PI and PET). Microscopy and spectroscopy showed that the printed metal is nanocrystalline, solid with no porosity and with low impurities. Electrical resistivity close to the bulk (~2-time) was obtained without any thermal annealing. Mechanical characterization confirmed excellent cyclic strength of the deposited metal, with limited degradation under high cyclic flexure. Several devices including radio frequency identification (RFID) tag, heater, strain gauge, and temperature sensor are demonstrated.
Highlights
Additive printing processes are promising for low-cost and more versatile device fabrication on flexible substrates in comparison with the conventional fabrication processes such as photolithography and high vacuum processes
Conductive inks with a “built-in” sintering mechanism, which is triggered during drying of the printed pattern have been demonstrated
Apart from direct ink writing (DIW) and electrohydrodynamic printing (EHD) process, other available microscale metal printing processes such as laser-induced forward transfer (LIFT) and laser-induced photoreduction (LIPR) use a laser, which may not be compatible with flexible substrates
Summary
Achieve electrical conductivity equivalent to that of the bulk silver after sintering at 90 °C18. Compared to DIW and EHD, this process results in pure metal with no binders or solvents, and does not require sintering or annealing Using this process, we demonstrate potential applications for direct printing of radio frequency identification (RFID) tag, heater, strain gauge, and temperature sensor on flexible substrates (Fig. 1D–G). We characterized changes in electrical resistance of the printed metal patterns on polymer substrate under cyclic loading. The EDS spectra of Cu shows a small www.nature.com/scientificreports/ A Ni
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