A combined finite-discrete element model for elasto-capillary phenomena

Elasto-capillary phenomena, involving finite deformation of elastomer and elasto-capillary effect of droplet/film, widely exist in biological and micro-electro-mechanical systems. To quantitatively analyze the influence of surface tension and to accurately predict the deformation of elastomer, we develop a finite strain model of hyperelastic materials, and then solve it by the explicit dynamics employing the combined finite -discrete element method (FDEM). Based on our model, we investigate the expansion of a small cavity in elastomer and examine the relation between radius and pressure of cavity. Besides, we explore the deformation of an elastic rod that is immersed in liquid and subjected to surface tension. Results show that when the elasto-capillary effect is neglected, edges of the rod would be unrealistically roughened, while the surface is actually smoothed as the surface tension increases. Moreover, we explore the elasto-capillary effect on advanced multiple-period wrinkling patterns in both planar and curved film-substrate systems, showing that the rough wavy surface can be smoothed by increasing surface tension. Our results not only provide fundamental insights into a variety of elasto-capillary phenomena, but also offer a platform to quantitatively guide rational designs of flexible smart devices actuated by surface tension.