**2.4 Geometry design and fabrication**

Six different prototypes of micromixers were designed with different microchannel geometries for the reaction chambers. This was achieved by varying the number of layers of PMMA sheets required to create the channel. In the case of one layer, the channel geometry was circular and triangular. In contrast the assembly of multiple layers enabled rectangular-3D, one loop, two horizontal loops, and two vertical loops (See **Figure 1**).

For the micromixers manufacture, each design was engraved and cut on sheets of polymethylmethacrylate (PMMA), with a thickness of 3 mm and an area of 75x25 mm, using a Speedy 100, 60 W laser cutting system (TROTEC, Germany). Sheets were glued together to assemble the devices by applying a few drops of 96% ethanol on the contacting surfaces and maintaining a constant pressure for 8 minutes at 105 °C.
