Figure 2.

Complex laminar flow patterns in a single open channel can be controlled using multiple paper micro channels. (a) A chip was fabricated with a microchannel that has a Y junction on either end, connecting to a reservoir of fluorescein and a reservoir of water on the left and paper microchannels on the right. By modifying the length L₁ and L₂ of the paper microchannels to the wick, the width w₂ and w₁ of the fluorescein-stained and the unstained lamina, respectively, can be modified. (b) The ratio w₂/w₁ varies linearly with the ratio of the paper microchannel lengths L₁/L₂.in agreement with Darcy's law (R² = 0.8996). (c) This trend is consistent with that observed by directly varying the ratio of the flow rates Φ₂ and Φ₁, using syringe pumps. The scale bar is 50 μm.