Effects of encapsulation elasticity on the stability of an encapsulated microbubble
Effects of encapsulation elasticity on the stability of an encapsulated microbubble
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DOI：
10.1016/j.jcis.2009.05.019
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发表时间：
2009-08-15
影响因子：
9.9
通讯作者：
Jain, Pankaj
中科院分区：
文献类型：
--
作者：
Katiyar, Amit;Sarkar, Kausik;Jain, Pankaj
开发并研究了一种气体从封装微泡传输到周围介质的模型，并结合封装弹性的影响进行了研究。封装弹性可稳定微泡以防止溶解，并解释了微泡造影剂的长保质期。我们考虑气泡以及含有全氟化碳气体的气泡。确定饱和度、表面张力和界面膨胀弹性之间的分析条件以获得这些微泡的非零平衡半径。方程的数值解验证了平衡半径的稳定性。在不饱和介质中，所有封装的气泡都会溶解。在饱和介质中，当界面膨胀弹性大于平衡表面张力时，封装的气泡可实现长期稳定的半径。对于界面膨胀弹性小于平衡表面张力的气泡，只有当饱和度大于临界值时，才能实现非零半径的稳定气泡。即使它们最初含有空气以外的气体，达到稳定半径的气泡最终也会变成气泡。该模型应用于八氟丙烷填充的脂质涂层 2.5 μm 气泡，该气泡在达到平衡尺寸之前由于进气而表现出短暂的膨胀。研究并讨论了弹性、壳渗透性、初始摩尔分数、初始半径和饱和度的影响。壳渗透率和摩尔分数不影响微泡的最终平衡半径，但影响时间尺度和瞬态动力学。类似地，平衡半径与初始半径的比率仍然不受初始半径变化的影响。 (C) 2009 Elsevier Inc. 保留所有权利。
A model for gas transport from an encapsulated microbubble into the surrounding medium is developed and investigated incorporating the effects of encapsulation elasticity. Encapsulation elasticity stabilizes microbubbles against dissolution and explains the long shelf life of microbubble contrast agent. We consider air bubbles as well as bubbles containing perfluorocarbon gas. Analytical conditions between saturation level, Surface tension and interfacial dilatational elasticity are determined for attaining non-zero equilibrium radius for these microbubbles. Numerical solution of the equation verifies the stability of the equilibrium radii. In an undersaturated medium all encapsulated bubbles dissolve. In a saturated medium, an encapsulated bubble is found to achieve a long-time stable radius when interfacial dilatational elasticity is larger than equilibrium surface tension. For bubbles with interfacial dilatational elasticity smaller than the equilibrium surface tension, stable bubble of non-zero radius can be achieved only when the saturation level is greater than a critical value. Even if they initially contain a gas other than air, bubbles that reach a stable radius finally become air bubbles. The model is applied to an octafluoropropane filled lipid-coated 2.5 mu m bubble, which displayed a transient swelling due to air intake before reaching an equilibrium size. Effects of elasticity, shell permeability, initial mole fraction, initial radius and saturation level are investigated and discussed. Shell permeability and mole fraction do not affect the final equilibrium radius of the microbubble but affect the time scale and the transient dynamics. Similarly, the ratio of equilibrium radius to initial radius remains unaffected by the variation in initial radius. (C) 2009 Elsevier Inc. All rights reserved.