Abstract
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.
Highlights
Fluid flow in the channels of microfluidic devices has most commonly been controlled using high precision mechanical pumps.[14]
We investigate the effect of applied voltage, solution viscosity and electrical conductivity on the production of microbubbles and their characteristics
Many of the key characteristics of microbubbles are directly related to their size and in this work we have presented a new technique for microbubble formation which offers excellent control over bubble size and polydispersity, continuous production with lower risk of clogging and the potential for multiplexing to achieve higher production rates
Summary
Fluid flow in the channels of microfluidic devices has most commonly been controlled using high precision mechanical pumps.[14] another type of flow in microchannels, broadly refrered to as electroosmotic flow,[15] initiated by the application of an electric field, has been studied extensively.[16] This method of driving and controlling the operating fluid, has some distinct advantages due to the localization of the electrical forces in these miniaturized devices. High electric fields can be obtained with relative ease and they can assist with the flow of fluids in the microchannels.[17] in order to alleviate the difficulties of excessive pressure gradients associated with microfluidic pumps in microchannels, pressure driven flows are often replaced by electroosmotic flows.[18]. Kim et al.[20] developed a microchip droplet generator using an electrohydrodynamic actuation method
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