Rapoport Natalya Y, Efros Alexey L, Christensen Douglas A, Kennedy Anne M, Nam Kweon-Ho
Department of Bioengineering, University of Utah, Salt Lake City, UT 84112, USA.
Bubble Sci Eng Technol. 2009;1(1-2):31-39. doi: 10.1179/175889709X446516.
The paper describes droplet-to-bubble transition in block copolymer stabilized perfluoropentane nanoemulsions. Three physical factors that trigger droplet-to-bubble transition in liquid emulsions and gels were evaluated, namely heat, ultrasound, and injections through fine-gauge needles. Among those listed, ultrasound irradiation was found the most efficient factor. Possible mechanisms of bubble generation and growth discussed in the paper include liquid-to-gas transition inside the individual bubble; bubble coalescence; and diffusion of dissolved air and/or perfluoropentane from small bubbles into larger bubbles (i.e., Oswald ripening). The last two factors result in irreversibility of the droplet-to-bubble transition. In gel matrices, ultrasound-induced droplet-to-bubble transition was substantially inhibited but was catalyzed by large (hundred micron) pre-existing bubbles irradiated by low frequency (hundred kilohertz) ultrasound. The dependence of the droplet-to-bubble transition on initial bubble size is theoretically treated and the role of increase of surface area in promoting bubble coalescence is discussed. Therapeutic implications of observed effects are discussed.
该论文描述了嵌段共聚物稳定的全氟戊烷纳米乳液中的液滴到气泡的转变。评估了引发液体乳液和凝胶中液滴到气泡转变的三个物理因素，即热、超声和通过细针注射。在所列因素中，超声辐照被发现是最有效的因素。论文中讨论的气泡产生和生长的可能机制包括单个气泡内的液-气转变；气泡聚并；以及溶解的空气和/或全氟戊烷从小气泡扩散到大气泡中（即奥斯特瓦尔德熟化）。最后两个因素导致液滴到气泡转变的不可逆性。在凝胶基质中，超声诱导的液滴到气泡转变受到显著抑制，但由低频（几百千赫兹）超声辐照的大（几百微米）的预先存在的气泡催化。从理论上探讨了液滴到气泡转变对初始气泡尺寸的依赖性，并讨论了表面积增加在促进气泡聚并中的作用。还讨论了观察到的效应的治疗意义。
