Paper-based writing electronics has received a lot of interest recently due to its potential applications in flexible electronics. To obtain ultra-low resistivity paper-based writing electronics, we developed a kind of ink with high concentration of Ag Nano-particles (up to 80 wt%), as well as a related dispensing writing system consisting an air compressor machine and a dispenser. Additionally, we also demonstrated the writability and practical application of our proposed ink and writing system. Based on the study on the effect of sintering time and pressure, we found the optimal sintering time and pressure to obtain high quality Ag NPs wires. The electrical conductivity of nano-silver paper-based electronics has been tested using the calculated resistivity. After hot-pressure sintering at 120 °C, 25 MPa pressure for 20 minutes, the resistivity of silver NPs conductive tracks was 3.92 × 10−8 (Ωm), only 2.45 times of bulk silver. The mechanical flexibility of nano-silver paper-based electronics also has been tested. After 1000 bending cycles, the resistivity slightly increased from the initial 4.01 × 10−8 to 5.08 × 10−8 (Ωm). With this proposed ink preparation and writing system, a kind of paper-based writing electronics with ultra-low resistivity and good mechanical flexibility was achieved.

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A silver nanoparticle sintering method is promising for the fabrication of flexible electronics. An ultrasonic-assisted sintering process is presented to obtain conductive patterns with low resistivity on a paper-based substrate. Compared to the conventional hot-pressing sintering process, the proposed method can efficiently fabricate densified microstructures with better electrical properties at low temperature and pressure. In particular, the effects of ultrasonic effective time, entry time, and amplitude were systematically analyzed. It was found that lower resistivity preferred larger ultrasonic amplitude. The ultrasonic effective time happened during the first 3 min of the entire sintering process, which implied that the ultrasonic synergetic effect occurred at the very beginning stage of the sintering process. Additionally, better conductivity of the sintered patterns was obtained when the ultrasonic entry time was shorter. The mechanism of the synergetic effect of ultrasonic sintering was also discussed in terms of vibration and cyclic stress perspectives. The proposed ultrasonic-assisted sintering method is believed to provide insights for the fabrication of flexible electronics.