Droplet interface bilayers are a convenient model system to study the physio-chemical properties of phospholipid bilayers, the major component of the cell membrane. The mechanical response of these bilayers to various external mechanical stimuli is an active area of research because of its implications for cellular viability and the development of artificial cells. In this article, we characterize the separation mechanics of droplet interface bilayers under step strain using a combination of experiments and numerical modelling. Initially, we show that the bilayer surface energy can be obtained using principles of energy conservation. Subsequently, we subject the system to a step strain by separating the drops in a step-wise manner, and track the evolution of the bilayer contact angle and radius. The relaxation time of the bilayer contact angle and radius along with the decay magnitude of the bilayer radius were observed to increase with each separation step. By analysing the forces acting on the bilayer and the rate of separation, we show that the bilayer separates primarily through the peeling process with the dominant resistance to separation coming from viscous dissipation associated with corner flows. Finally, we explain the intrinsic features of the observed bilayer separation by means of a mathematical model comprising the Young–Laplace equation and an evolution equation. We believe that the reported experimental and numerical results extend the scientific understanding of lipid bilayer mechanics, and that the developed experimental and numerical tools offer a convenient platform to study the mechanics of other types of bilayers.

液滴界面双层是研究磷脂双层（细胞膜的主要组成部分）的理化性质的便捷模型系统。这些双层对各种外部机械刺激的机械响应是一个活跃的研究领域，因为它对细胞活力和人造细胞的发育具有影响。在本文中，我们结合实验和数值模拟来表征阶跃应变下液滴界面双层的分离力学。最初，我们证明双层表面能可以利用能量守恒原理获得。随后，我们通过逐步分离液滴的方式使系统承受阶跃应变，并跟踪双层接触角和半径的演变。观察到双层接触角和半径的弛豫时间以及双层半径的衰减幅度随着每个分离步骤而增加。通过分析作用在双层上的力和分离速率，我们表明双层主要通过剥离过程分离，分离的主要阻力来自与角流相关的粘性耗散。最后，我们通过由杨-拉普拉斯方程和演化方程组成的数学模型解释了观察到的双层分离的内在特征。我们相信，所报告的实验和数值结果扩展了对脂质双层力学的科学理解，并且开发的实验和数值工具为研究其他类型双层的力学提供了便利的平台。