Overview of the 3D hydrodynamic focusing microfluidic mixer. (a) Schematic cross-section of the monolithic fused silica chip which shows the three fluid inlets and one main outlet for reactants. The polyimide capillary region of the mixer is compatible with X-ray spectroscopy. Note that the leftmost probe inlet was filled with water and sealed (i.e. permitted no liquid flow) in simulations and experiments for the current work. (b) Schematic view of the mixer and X-ray beam showing critical features and dimensions. The x = 0 position is indicated by the intersection of the red and green arrows. The schematic is topologically accurate but not to scale and aspect ratios have been exaggerated.