Perfluorocarbon (PFC) droplets are used in acoustic droplet vaporization (ADV), a phenomenon where droplets vaporize into gas microbubbles under exposure to ultrasound. The size and the size distribution of a phase change contrast agent is an important factor in determining the ADV threshold and the biodistribution. Thus, high throughout manufacturing of uniform-sized droplets, required to maintain spatial control of the vaporization process, remains challenging. This work describes a parametric evaluation of a novel process using premix membrane emulsification (PME) to produce homogeneous PFC emulsions at high rate with moderate pressure using Shirasu Porous Glass (SPG) membranes. In this study, we investigated the effect of several process parameters on the resulting pressure and droplet size: membrane pore size, flow rate, and dispersed phase type. The functionality of the manufactured emulsions for ADV was also demonstrated. Vaporization of the PFC emulsions was obtained using an imaging ultrasound transducer at 7.813 MHz, and the ADV thresholds were determined. Here, the pressure threshold for ADV was determined to be 1.49 MPa for uniform-sized perfluorohexane (PFHex) droplets with a mean size of 1.51 μm and a sharp distribution (CV and span respectively of 20% and 0.6). Thus, a uniform-sized droplet showed a more homogeneous vaporization with a uniform response in the focal region of the transducer. Indeed, polydispersed droplets had a more diffuse response outside the focal region due to the presence of large droplets that vaporize at lower energies. The ADV threshold of uniform-sized PFC droplets was found to decrease with the droplet diameter and the bulk fluid temperature, and to increase with the boiling temperature of PFC and the presence of an oil layer surrounding the PFC core.

中文翻译：

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通过预混膜乳化制备全氟化碳乳液，用于生物医学应用中的声学液滴汽化 (ADV)。

全氟化碳 (PFC) 液滴用于声学液滴蒸发 (ADV)，这是一种液滴在暴露于超声波下蒸发成气体微泡的现象。相变造影剂的大小和大小分布是决定 ADV 阈值和生物分布的重要因素。因此，维持蒸发过程的空间控制所需的均匀尺寸液滴的高贯穿制造仍然具有挑战性。这项工作描述了使用预混膜乳化 (PME) 以高速和中等压力使用 Shirasu 多孔玻璃 (SPG) 膜生产均质 PFC 乳液的新工艺的参数评估。在这项研究中，我们研究了几个工艺参数对产生的压力和液滴尺寸的影响：膜孔径、流速、和分散相类型。还展示了制造的 ADV 乳液的功能。使用成像超声换能器在 7.813 MHz 下获得 PFC 乳液的汽化，并确定 ADV 阈值。在这里，平均尺寸为 1.51 的均匀大小的全氟己烷 (PFHex) 液滴的 ADV 压力阈值被确定为 1.49 MPaμ m 和尖锐分布（CV 和跨度分别为 20% 和 0.6）。因此，均匀大小的液滴在换能器的焦点区域显示出更均匀的汽化和均匀的响应。事实上，由于存在在较低能量下蒸发的大液滴，多分散液滴在焦点区域外具有更扩散的响应。发现均匀尺寸的 PFC 液滴的 ADV 阈值随着液滴直径和整体流体温度的增加而降低，并随着 PFC 的沸腾温度和 PFC 核心周围油层的存在而增加。