Dynamics of bubble breakup with partly obstruction in a microfluidic T-junction Xiaoda Wang, Chunying Zhu, Yining Wu, Taotao Fu n , Youguang Ma n State Key Laboratory of Chemical Engineering, Collaborative Innovation Center of Chemical science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China HIGHLIGHTS  Bubble breakup with partly obstruc- tion in a T-junction is studied.  The variation of the minimum width of the neck during bubble breakup is studied.  The bubble breakup process includes squeezing stage and pinch-off stage.  A tunnel characterizing the bubble breakup with partly obstruction is highlighted.  The leakage volume for the breakup process is calculated. GRAPHICAL ABSTRACT article info Article history: Received 29 January 2015 Received in revised form 20 April 2015 Accepted 23 April 2015 Available online 4 May 2015 Keywords: Bubble Breakup Microfluidic Multiphase flow Interface Hydrodynamics abstract The bubble breakup with partly obstruction in a microfluidic T-junction was investigated experimentally in this paper. It was demonstrated that the breakup process could be divided into two stages: squeezing stage and pinch-off stage, according to the evolution of the minimum width of the bubble neck w m . During the squeezing stage, the variation of 1 w m /w c with time t could be scaled by a power law. In the pinch-off stage, the minimum width of the bubble neck w m could also be correlated into a power law function with the remaining time (T c t). A tunnel, which characterized the bubble breakup with partly obstruction, appeared between the bubble tip and the microchannel wall in the squeezing stage, and exhibited little effect on the evolution of the bubble neck. However, the evolution of the bubble tip was obviously different before and after tunnel appearance. By means of the analysis on the dynamics of the bubble tip, some important parameters such as the final bubble length and the leakage volume were studied and discussed. & 2015 Elsevier Ltd. All rights reserved. 1. Introduction The microfluidic technology has attracted increasing attention over the last two decades due to its broad development prospects (Brown et al., 2014; Hol and Dekker, 2014; Nge et al., 2013). The multiphase microfluidic technique, one of the most important branches of microfluidic technology, is characterized by its ability to continuously produce highly monodisperse droplets or bubbles. Such feature has made the microfluidic technique applied to various domains, such as high throughput screening (Schudel et al., 2013), chemical synthesis (Elvira et al., 2013), drug development (Wu et al., 2014) and crystallization (Puigmarti-Luis, 2014). The T-junction is one of the most common geometries of microfluidic devices, as it could help scientists and engineers to facilely control the bubble or droplet behaviors. One of the basic abilities of the T-junction is to generate micro-bubbles or micro- droplets. Up to now, both the bubble and droplet formation mechanisms in T-junctions have been widely studied by the theoretical analyses, experimental observations and numerical simulations (Christopher et al., 2008; de Menech et al., 2008; Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/ces Chemical Engineering Science http://dx.doi.org/10.1016/j.ces.2015.04.038 0009-2509/& 2015 Elsevier Ltd. All rights reserved. n Corresponding authors. E-mail addresses: ttfu@tju.edu.cn (T. Fu), ygma@tju.edu.cn (Y. Ma). Chemical Engineering Science 132 (2015) 128–138