The western blot is a widely used analytical technique aimed at detecting specific proteins in the given sample of tissue homogenate or extract.1 Though the conventional western blot has been routine in determining the molecular weight of a protein, the current trend in protein analysis is to simultaneously detect multiple proteins in one single run.2,3 To achieve this goal, we have developed a method that combines a microfluidic immunoassay with conventional protein blotting, which we call microfluidic western blot (μWB), to analyze the expression and molecular weight of multiple proteins within one sample.