*Microfluidics for Time-Resolved Small-Angle X-Ray Scattering DOI: http://dx.doi.org/10.5772/intechopen.95059*

All experiments require planning and consideration of the simultaneous use of analysis, mixing and cleaning equipment due to the generally small dimensions of microfluidic devices. In the past decades, a very diverse range of microfluidic reactor devices have been designed for time-resolved studies of reactions. Designs such as continuous-flow, stopped-flow, droplet-based and digital microfluidics have been developed and applied to produce materials with sizes ranging from nanometres to almost millimetres. In this chapter, we are focusing on continuous and stopped flow devices, in particular on hydrodynamic focusing techniques. In comparison to droplet-based techniques, hydrodynamic focusing is a straightforward approach to implement, due to its pure hydrodynamic principles. It only includes surface tension effects at the liquid–liquid interface in the outlet channel of the microfluidic device without the need of consideration of surface tension effects at liquid–gas interfaces. These devices offer stability at high flowrates, allow highthroughput applications and enable highly controllable operational conditions, as the flow behaviour is the only influential parameter that needs to be considered for time-resolved studies.
