A microfluidic route to small CO₂microbubbles with narrow size distribution

Abstract

We report a new microfluidic strategy for the generation of small (<10 mm) microbubbles with a narrow size distribution. Our approach has the following features: (i) the generation of bubbles from gaseous CO 2 and (ii) the controllable dissolution of these bubbles until they reach a desired size. We examine the role of various factors on the formation and the extent of bubble dissolution and show that the final dimensions of bubbles are determined by the flow rate of the continuous aqueous phase and the acid-base equilibria established within the microchannels.

Uniform yeast cell assembly via microfluidics

“…Generally, greater bubble volume reductions were achieved at high pH. 37 This was validated in our observation that no stable yeast-armored bubbles were generate at neutral pH due to lack of bubble shrinkage. Extreme pH condition (>13), on the hand, was avoided as it might compromise cell functionality.…”

“…We adopted here a strategy used in the microfluidic formation of stable, monodisperse, colloid-armored microbubbles-using rapid CO 2 dissolution followed by its reactions in basic solutions that leads to bubble shrinkage, 36,37 and hence quickly increases surface coverage of the yeast cells as the total gas-aqueous interfacial area reduces. Fig.…”

Three-Dimensional Electro-Sonic Flow Focusing Ionization Microfluidic Chip for Mass Spectrometry

“…For the 2D micro-channel, most research efforts have focused on the low viscosity ratio of the dispersed phase and continuous phase, such as water in oil [41] and air in water [47]. For comparison, a corresponding 2D micro-channel was fabricated in this paper and the high viscosity ratio of the dispersed phase and continuous phase was performed.…”

“…However, the fabrication processes were complicated and coupling such devices with other microfluidic modules was difficult. For microfluidic FF, two-dimensional (2D) microfluidic FF chips always require dispersed and continuous phases with low viscosity ratios (approximately 0.1) [55], such as water in oil [41] and air in water [47]. The high viscosity ratio is also barely implemented because the 2D micro-channel will form a shear flow and the dispersed phase will not break [56][57][58][59].…”

“…Inspired by flow focusing (FF) technology [41][42][43][44][45][46][47][48][49], we designed an inner electrospray nozzle that has a Taylor cone at the front end of the liquid (dispersed phase) channel focused by the air (continuous phase) inside the microfluidic chip. This water in the air FF regime was first implemented by using a coaxial capillary tube closed to a small hole in a thin plate [50][51][52][53][54].…”