In order to fully exploit the outstanding mass transfer characteristics of liquid-liquid slug flow in capillaries for technical extraction processes, it is necessary to employ numbering-up to retain the underlying benefits of microscale operation. For optimal performance, each of the parallelized capillaries should be operated at the same flow rate, a similar phase ratio and with a single, uniform slug structure. Since the fabrication tolerances of microstructures make it difficult to construct distributors generating the uniform multiphase flow sought, a simple and affordable scheme for monitoring and regulating the slug flow in individual capillaries has been developed. The concept was implemented successfully for both simple aqueous-organic biphasic flows and with more challenging systems exhibiting flow multiplicities as a consequence of viscosity changes.