Bundeswehr Universität München, Neubiberg, Germany.
Biomicrofluidics. 2012 Oct 24;6(4):44104. doi: 10.1063/1.4762854. eCollection 2012.
Electrosprays are a powerful technique to generate charged micro/nanodroplets. In the last century, the technique has been extensively studied, developed, and recognized with a shared Nobel price in Chemistry in 2002 for its wide spread application in mass spectrometry. However, nowadays techniques based on microfluidic devices are competing to be the next generation in atomization techniques. Therefore, an interesting development would be to integrate the electrospray technique into a microfluidic liquid-liquid device. Several works in the literature have attempted to build a microfluidic electrospray with disputable results. The main problem for its integration is the lack of knowledge of the working parameters of the liquid-liquid electrospray. The "submerged electrosprays" share similar properties as their counterparts in air. However, in the microfluidic generation of micro/nanodroplets, the liquid-liquid interfaces are normally stabilized with surface active agents, which might have critical effects on the electrospray behavior. In this work, we review the main properties of the submerged electrosprays in liquid baths with no surfactant, and we methodically study the behavior of the system for increasing surfactant concentrations. The different regimes found are then analyzed and compared with both classical and more recent experimental, theoretical and numerical studies. A very rich phenomenology is found when the surface tension is allowed to vary in the system. More concretely, the lower states of electrification achieved with the reduced surface tension regimes might be of interest in biological or biomedical applications in which excessive electrification can be hazardous for the encapsulated entities.
电喷雾是一种产生带电微/纳米液滴的强大技术。在上个世纪，该技术得到了广泛的研究、开发和认可，并因其在质谱分析中的广泛应用而在 2002 年共同获得了诺贝尔化学奖。然而，如今基于微流控器件的技术正在竞争成为下一代雾化技术。因此，将电喷雾技术集成到微流控液-液装置中是一个有趣的发展方向。文献中有几项工作试图构建一种带有争议结果的微流控电喷雾。其集成的主要问题是缺乏对液-液电喷雾工作参数的了解。“浸没式电喷雾”具有与空气中的同类物相似的特性。然而，在微流控微/纳米液滴的产生中，液-液界面通常用表面活性剂稳定，这可能对电喷雾行为产生关键影响。在这项工作中，我们综述了在没有表面活性剂的液体浴中浸没式电喷雾的主要性质，并系统地研究了该系统在表面活性剂浓度增加时的行为。然后分析并比较了所发现的不同状态与经典和更新的实验、理论和数值研究。当允许系统中的表面张力变化时，会发现非常丰富的现象学。更具体地说，在表面张力降低的状态下实现的较低的带电状态可能在生物或生物医学应用中具有吸引力，因为过度带电可能对被包裹的实体造成危害。
