FIG. 3.

Channels with a semi-elliptical cross-section and a localised contraction fabricated via pasta templating. (a) Grinding tool subtracts a section of the pasta to create a localised contraction. (b) Top view of PDMS channel filled with blue stained water, emphasising the contracted shape with no leakage. (c) Snapshots of the filling process with blue stained water in a pre-filled water channel, showing flow acceleration at the narrowed passage. Dashed lines indicate point of dissection of the channel, to show the (d) semi-elliptical cross-section outside the contraction and (e) quarter-elliptical cross-section at the apex of the contraction. (f) Velocity contours of flow at various cross-sections of the channel, obtained at a flow rate of 50 μl/min.