Department of Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK.
Lab Chip. 2014 Jul 21;14(14):2437-46. doi: 10.1039/c4lc00328d.
This work investigates the generation of monodisperse microbubbles using a microfluidic setup combined with electrohydrodynamic processing. A basic T-junction microfluidic device was modified by applying an electrical potential difference across the outlet channel. A model glycerol air system was selected for the experiments. In order to investigate the influence of the electric field strength on bubble formation, the applied voltage was increased systematically up to 21 kV. The effect of solution viscosity and electrical conductivity was also investigated. It was found that with increasing electrical potential difference, the size of the microbubbles reduced to ~25% of the capillary diameter whilst their size distribution remained narrow (polydispersity index ~1%). A critical value of 12 kV was found above which no further significant reduction in the size of the microbubbles was observed. The findings suggest that the size of the bubbles formed in the T-junction (i.e. in the absence of the electric field) is strongly influenced by the viscosity of the solution. The eventual size of bubbles produced by the composite device, however, was only weakly dependent upon viscosity. Further experiments, in which the solution electrical conductivity was varied by the addition of a salt indicated that this had a much stronger influence upon bubble size.
本工作研究了使用微流控装置结合电动力学处理来生成单分散微泡的方法。通过在出口通道上施加电势差，对基本的 T 形微流控装置进行了修改。选择模型甘油-空气体系进行实验。为了研究电场强度对气泡形成的影响，系统地将施加的电压增加到 21 kV。还研究了溶液粘度和电导率的影响。结果发现，随着外加电势差的增加，微泡的尺寸减小到毛细管径的约 25%，而其尺寸分布仍然很窄（多分散指数约为 1%）。发现当外加电势差超过 12 kV 时，微泡的尺寸不再显著减小。结果表明，在 T 形结（即在没有电场的情况下）中形成的气泡的大小强烈地受到溶液粘度的影响。然而，复合装置产生的气泡的最终大小仅与粘度弱相关。进一步的实验表明，通过添加盐来改变溶液的电导率对气泡尺寸有更强的影响。
