Schematic of the mixing plate and mixer assembly used for continuous-flow mixing. (a) An enlarged view of the mixing region is shown. The 100 µm-wide section is the observation region with Kapton windows. Other parts are covered by stainless steel plates precisely machined to match the observation region and seal the mixing region. Channels are 30 µm wide in the mixing region and 100 µm wide in the observation region. (b) The assembly of the mixing plate; Kapton windows and matching stainless steel plates are shown. The unit is held together with pressure applied to the 12.5 mm-thick top and bottom stainless steel plates (shown in dark blue). Stainless steel guide pins were used on the base plate to keep the three precisely wire-EDM machined plates in register to within 10 µm during assembly.