Liquid metal particle popping: Macroscale to nanoscale

Liquid metal nanoparticles can be used to produce stretchable electronic devices. Understanding the mechanical properties of liquid metal nanoparticles is crucial to optimizing their use in various applications, especially printing of flexible, stretchable electronics. Smaller nanoparticles are desired for high-resolution printing and compatibility with existing scalable manufacturing methods; however, they contain less liquid metal and are more difficult to rupture than larger particles, making them less desirable for post-processing functionality. This study investigates the mechanics of liquid metal particle rupture as a function of particle size. We employ compression of particle films to characterize the composition of the particle core and derive a minimum particle size required to achieve sintering and subsequent conductance. We further derive the force required to rupture a single particle and validate the results by rupturing individual nanoparticles using atomic force microscopy. Finally, we relate the liquid metal nanoparticles to isotropically-elastic thin-shell microspheres to approximate the particle shell stiffness. An increased understanding of the behavior of liquid metal nanoparticles during rupture reveals limitations of current manufacturing processes and paves the way for the next generation of scalable mass-producible soft electronics using additive manufacturing technologies. (C) 2017 Elsevier Ltd. All rights reserved.