On the micromechanics of gallium-based droplets embedded in elastomers

Gallium-based liquid metal elastomer composites (LMECs) have attracted increased attention in the fields of stretchable electronics, soft robots and sensors owing to their combination of superb functionalities and fluidity. A comprehensive understanding of the micromechanics of LM droplets within the elastomer matrix is instrumental in establishing the structure-property relationship of LMECs. It is imperative to observe the micro-deformation process of LM droplets along with the surrounding matrix under the applied loading, whereby the synergic mechanisms between the droplets and soft matrix are revealed. In this study, in-situ loading experiments were conducted to ascertain the deformation evolution of single droplet and the interaction between paired droplets on their micro-strain fields. The level of difficulty in droplet deformation under different configurations was analyzed, alongside the evolution of their aspect ratio with the applied stretch ratio. At the same time, FEM simulations were implemented in order to analyze the hoop strain distribution and droplet aspect ratio as a function of the applied strain. The experimental and simulation results indicated that the normally adopted affine transformation between the droplets and the macroscopic applied strain was not satisfied for the dilute droplet in the composites. Furthermore, the orientation of paired droplets significantly influenced the micro-strain fields within the droplets, which is attributable to the interference effect among the displacement fields. The present research is constructive to interpreting the evolution of mechanical and functional performances of LMECs during finite strain deformation.