The Role of Contact Line (Pinning) Forces on Bubble Blockage in Microchannels.
The Role of Contact Line (Pinning) Forces on Bubble Blockage in Microchannels.
复制标题
DOI：
10.1115/1.4029033
复制
发表时间：
2015-03
期刊：
影响因子：
--
通讯作者：
M. Mohammadi;K. Sharp
中科院分区：
文献类型：
--
作者：
M. Mohammadi;K. Sharp
本文着重研究了接触线(钉扎力)对微通道中干气泡迁移率的影响。以低于表面液体除湿速度的速度运动的气泡基本上是干燥的，这意味着气泡周围没有薄薄的液膜。对于这些“干”气泡，接触线力和由钉扎引起的可能的毛细压力梯度作用于气泡并抵抗运动。如果没有足够的驱动力(如外部压力)，干泡就会停滞不前。首次提出了一个两部分理论模型，该模型估计了具有凹背和凸背界面的滞留气泡克服接触线力和刺激运动所需的压差。为了验证我们的理论，测量了在呈现接触角滞后的方形微通道中移动单个干气泡所需的压力。工作液为去离子水。在不同表面亲水性的镀膜玻璃通道上进行了实验，得到了气泡的凹面和凸面。实验结果与模型对正方形流道的预测相吻合。凹背模型和凸背模型的预测值分别在实验值的19%和27%以内。
This paper highlights the influence of contact line (pinning) forces on the mobility of dry bubbles in microchannels. Bubbles moving at velocities less than the dewetting velocity of liquid on the surface are essentially dry, meaning that there is no thin liquid film around the bubbles. For these "dry" bubbles, contact line forces and a possible capillary pressure gradient induced by pinning act on the bubbles and resist motion. Without sufficient driving force (e.g., external pressure), a dry bubble is brought to stagnation. For the first time, a bipartite theoretical model that estimates the required pressure difference across the length of stagnant bubbles with concave and convex back interfaces to overcome the contact line forces and stimulate motion is proposed. To validate our theory, the pressure required to move a single dry bubble in square microchannels exhibiting contact angle hysteresis has been measured. The working fluid was deionized water. The experiments have been conducted on coated glass channels with different surface hydrophilicities that resulted in concave and convex back interfaces for the bubbles. The experimental results were in agreement with the model's predictions for square channels. The predictions of the concave and convex back models were within 19% and 27% of the experimental measurements, respectively.