Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA.
Lab Chip. 2014 Jul 21;14(14):2428-36. doi: 10.1039/c4lc00354c.
We studied the dissolution dynamics of CO2 gas bubbles in a microfluidic channel, both experimentally and theoretically. In the experiments, spherical CO2 bubbles in a flow of a solution of sodium dodecyl sulfate (SDS) first shrink rapidly before attaining an equilibrium size. In the rapid dissolution regime, the time to obtain a new equilibrium is 30 ms regardless of SDS concentration, and the equilibrium radius achieved varies with the SDS concentration. To explain the lack of complete dissolution, we interpret the results by considering the effects of other gases (O2, N2) that are already dissolved in the aqueous phase, and we develop a multicomponent dissolution model that includes the effect of surface tension and the liquid pressure drop along the channel. Solutions of the model for a stationary gas bubble show good agreement with the experimental results, which lead to our conclusion that the equilibrium regime is obtained by gas exchange between the bubbles and liquid phase. Also, our observations from experiments and model calculations suggest that SDS molecules on the gas-liquid interface form a diffusion barrier, which controls the dissolution behaviour and the eventual equilibrium radius of the bubble.
我们通过实验和理论研究了 CO2 气泡在微流道中的溶解动力学。在实验中，在十二烷基硫酸钠（SDS）溶液流动中，球形 CO2 气泡会先迅速收缩，然后达到平衡尺寸。在快速溶解阶段，达到新平衡所需的时间与 SDS 浓度无关，均为 30ms，而达到的平衡半径则随 SDS 浓度而变化。为了解释不完全溶解的现象，我们通过考虑已经溶解在水相中的其他气体（O2、N2）的影响来解释实验结果，并开发了一个包含表面张力和沿通道的液体压降影响的多组分溶解模型。对于静止气泡的模型解与实验结果吻合较好，这使我们得出结论，平衡状态是通过气泡和液相之间的气体交换来实现的。此外，我们从实验和模型计算中观察到，SDS 分子在气液界面形成扩散障碍，控制着气泡的溶解行为和最终的平衡半径。
