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Xingyun Yang1 Ximin He1

1, University of California, Los Angeles, Los Angeles, California, United States

Silver patterning is vital to achieve various functions in fields of electronics, optics and biomedical devices. State of the art relies on three main approaches to pattern silver: photolithography with masks, inkjet printing and selective laser sintering (SLS). However, all the three prevailing methods have some limitations. For example, introduction of mask complicates and slows down the whole manufacturing process; inkjet printing creates patterns in serial, which could be low efficient and energy consuming; abundant heat generated from laser could damage underlying substrates with low glass transition temperature (Tg), especially flexible substrates widely used for soft electronics. Therefore, it is urgent to develop a simple, quick and low-temperature method for silver patterning. Here, we introduce a silver printing technique utilizing photoreaction to in-situ generate patterned silver thin films under room temperature. Upon irradiation of patterned white light for around 20 min, photosensitive silver ink is simultaneously converted into and deposited patterned metallic silver on different substrates, such as PET film, PDMS, silicon wafer, etc. The printed silver patterns have high resolution up to 100 micron and a tunable printing area ranging from micrometer to meter size, both controllable by the digital light projecting system. The whole pattern forms at once as a plane rather than in serial, so that the fabrication time is significantly reduced, especially dealing with large patterns. Chemical annealing with strong electrolyte salt after printing process remarkably improves electrical conductivity of the printed silver patterns, reaching around 30% of bulk silver, which is sufficient enough for electricity conductance. Our silver patterning technique processing under room temperature shows great superiority in extending the choice for substrates to a broad variety of materials, notably flexible materials with low Tg. The excellent compatibility of our technique with flexible substrates provides a novel strategy to develop soft electronic devices. In general, the silver printing technology is a simple, facile and quick method to achieve silver patterning under room temperature with primitive device and easy manipulation. The printed silver patterns exhibit excellent electrical conductivity performance and high compatibility with various substrates, and the size and shape of the patterns are conveniently controllable by computer without rendering any physical masks.

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