Affiliation:
1. Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA
2. School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 01234, USA
3. Wyss Institute for Biologically Inspired Engineering, 52 Oxford St, Cambridge, Massachusetts 02138, USA
Abstract
Phospholipid bilayers are a major component of the cell membrane that is in contact with physiological electrolyte solutions including salt ions. The effect of salt on the phospholipid bilayer mechanics is an active research area due to its implications for cellular function and viability. In this manuscript, we utilize droplet interface bilayers (DIBs), a bilayer formed artificially between two aqueous droplets, to unravel the bilayer formation and separation mechanics with a combination of experiments and numerical modeling under the effects of K+, Na+, Li+, Ca2+, and Mg2+. Initially, we measured the interfacial tension and the interfacial complex viscosity of lipid monolayers at a flat oil–aqueous interface and show that both properties are sensitive to salt concentration, ion size, and valency. Subsequently, we measured DIB formation rates and show that the characteristic bilayer formation velocity scales with the ratio of the interfacial tension to the interfacial viscosity. Next, we subjected the system to a step strain by separating the drops in a stepwise manner. By tracking the evolution of the bilayer contact angle and radius, we show that salt influences the bilayer separation mechanics, including the decay of the contact angle, the decay of the bilayer radius, and the corresponding relaxation time. Finally, we explain the salt effect on the observed bilayer separation by means of a mathematical model comprising the Young–Laplace and evolution equations.
Subject
Condensed Matter Physics,Fluid Flow and Transfer Processes,Mechanics of Materials,Computational Mechanics,Mechanical Engineering
Cited by
2 articles.
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