Taylor bubble formation and flowing in a straight millimetric channel with a cross-junction inlet geometry Part II: Gas-liquid mass transfer

•Mass transfer was studied during bubble formation at a cross-junction.•Accuracy of resazurin-based technique was improved by advanced image systems.•Different mechanisms were observed for the developing O2 concentration fields.•Oxygen concentration fields were measured during and after bubble pinch-off.•A scaling law relating kLa and fc was proposed to gather literature data.