Abstract Inkjet printing of metal nanoparticle (NP) inks on various substrates is a novel additive manufacturing technology which has found widespread applications in flexible electronics. The printed NP inks need to be heated through laser sintering to obtain high electrical and mechanical properties. However, the heat transfer and diffusion mechanisms of metal nanoparticles during laser sintering have not been fully understood. In this study, a multiscale model combined transient heat transfer model and molecular dynamics (MD) model is developed to simulate the laser sintering process of silver NP inks. Our simulation results show that the local temperature in printed silver film in the laser spot increases significantly, while the temperature increase in the polyimide (PI) substrate is much lower, demonstrating the feasibility of laser sintering in flexible heat-sensitive substrates. To reveal the micro sintering mechanism, the configurational evolution of silver nanoparticles during laser sintering is observed using MD model. We found that the silver atoms on the nanoparticle surface diffuse into the interfaces between adjacent nanoparticles, forming sintered necks. These necks gradually grow, reducing electrical resistivity of the sintered nanostructures. In addition, the effects of laser parameters on the sintering performance are discussed. Both increasing laser power and decreasing scanning speed can improve sintering performance. However, the laser power is much more efficient than scanning speed in improving sintering performance. Our simulation method could be used to optimize the laser sintering process.

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喷墨印刷银纳米粒子油墨的激光烧结多尺度模拟研究

摘要 在各种基材上喷墨打印金属纳米粒子 (NP) 墨水是一种新型的增材制造技术，已在柔性电子产品中得到广泛应用。印刷的 NP 油墨需要通过激光烧结加热以获得高的电气和机械性能。然而，激光烧结过程中金属纳米颗粒的传热和扩散机制尚未完全了解。在这项研究中，开发了一种结合瞬态传热模型和分子动力学 (MD) 模型的多尺度模型来模拟银 NP 油墨的激光烧结过程。我们的模拟结果表明，激光光斑中印刷银膜的局部温度显着升高，而聚酰亚胺（PI）基板的温度升高要低得多，证明了激光烧结在柔性热敏基板上的可行性。为了揭示微烧结机制，使用 MD 模型观察了激光烧结过程中银纳米颗粒的构型演变。我们发现纳米颗粒表面的银原子扩散到相邻纳米颗粒之间的界面，形成烧结颈。这些颈部逐渐增长，降低了烧结纳米结构的电阻率。此外，还讨论了激光参数对烧结性能的影响。增加激光功率和降低扫描速度都可以提高烧结性能。然而，在提高烧结性能方面，激光功率比扫描速度更有效。我们的模拟方法可用于优化激光烧结过程。