Figure 5.

Volume-metered valve with a moveable metering pad. A. Schematic of the volume-metered flow-diversion switch showing transverse and lateral views. It consists of a metering pad with actuators inserted in it, resting on top of a flow channel. Actuators extend out of the metering pad into cavities on the surface. Firm contact between the flow channel and metering pad is ensured by a weight attached on top of the pad. Fluid in the channel flows into the metering pad initially, until actuators expand and lift the pad off. After actuation, fluid flows downstream the valve in the flow channel. The lateral view shows the schematic of this valve with two flow channels, A and B, with an adapter channel in between. B. Top and side views of the valve before (t = 15 min) and after (t = 38 min) actuation. Fluid flowed into the metering pad before actuation (t = 15 min; top view) and into channel B after actuation (t = 38 min; top view). Scale bar is 1 cm. Side view shows the sponge actuator before (t = 15 min) and after (t = 38 min) actuation. Scale bar is 1 mm. C. Flow rates (linear velocity) of fluid flowing into the metering pad (solid circles; red line) and channel B (hollow circles; green line) as a function of time. Graphs show steady flow into the metering pad and channel B, before and after actuation, respectively. There was slight leakage of fluid into channel B before actuation, between t = 18 and 25 min (dotted rectangle).