Perfluoropentane droplets with cellulose nanofibers (CNF) shells have demonstrated better stability and easier surface modification as ultrasound contrast agents and drug delivery vehicles. This paper presents a theoretical model assuming a four-phase state “inverse antibubble,” with the core filled with gas perfluoropentane surrounded by liquid perfluoropentane. A continuous, incompressible, and viscoelastic stabilizing layer separates the core from the surrounding water. A parametric study is performed to predict the frequency-dependent attenuation coefficient, the speed of sound, and the resonance frequency of the droplets which have a mean diameter of 2.47 ± 0.95 μm. Results reveal that the CNF-stabilized perfluoropentane droplets can be modeled in a Rayleigh-Plesset like equation. We conclude that the shell strongly influences the acoustic behavior of the droplets and the resonance frequency largely depends on the initial gas cavity radius. More specifically, the peak attenuation coefficient and peak-to-peak speed of sound decrease with increasing shear modulus, shear viscosity, and shell thickness, while they increase with increasing gas cavity radius and concentration. The resonance frequency increases as shear modulus and shell thickness increase, while it decreases as shear viscosity and gas cavity radius increase. It is worth mentioning that droplet concentration has no effect on the resonance frequency.

中文翻译：

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通过数值模拟获得具有粘弹性纤维素纳米纤维壳的全氟戊烷液滴的声学特性

具有纤维素纳米纤维 (CNF) 壳的全氟戊烷液滴已证明作为超声造影剂和药物输送载体具有更好的稳定性和更容易的表面改性。本文提出了一个假设四相状态“反反泡”的理论模型，核心充满气体全氟戊烷，周围环绕着液体全氟戊烷。一个连续的、不可压缩的、粘弹性的稳定层将核心与周围的水分开。进行参数研究以预测平均直径为 2.47 ± 0.95 μ的液滴的频率相关衰减系数、声速和共振频率 米。结果表明，CNF 稳定的全氟戊烷液滴可以用类似 Rayleigh-Plesset 的方程建模。我们得出结论，壳强烈影响液滴的声学行为，共振频率很大程度上取决于初始气腔半径。更具体地说，峰值衰减系数和峰峰值速度随着剪切模量、剪切粘度和壳厚度的增加而减小，而随着气腔半径和浓度的增加而增加。共振频率随着剪切模量和壳厚度的增加而增加，而随着剪切粘度和气腔半径的增加而降低。值得一提的是，液滴浓度对共振频率没有影响。