Capillary microvalve

In a centripetally-motivated fluid micromanipulation apparatus, a microsystem platform comprising

• a) a rotatable platform, comprising a substrate having a first flat, planar surface and a second flat, planar surface opposite thereto, each surface comprising a center about which the platform is rotated, wherein the first surface comprises in combination
• b) an entry port comprising a depression in the first surface having a volumetric capacity of about 1 to about 150 .mu.L, that is in direct fluid communication with
• c) a first metering capillary and a second overflow capillary, each being indirect fluid communication with the entry port, wherein each capillary defines a cross-sectional dimension of about 0.02 mm to about 1 mm, and wherein each capillary extends radially from the center of the platform and defines a first end proximally arrayed towards the center of the platform and a second end distally arrayed from the center of the platform, wherein the proximal end of each capillary defines a curved opening;
• wherein the first metering capillary defines a volume of the fluid and wherein the first metering capillary is fluidly connected with
• d) a first fluid chamber having a depth in the first surface of the platform equal to or greater than the metering capillary and positioned radially more distant from the center of the platform than the entry port, and the second overflow capillary is fluidly connected with
• e) an overflow chamber having a depth in the surface of the platform equal to or greater than the overflow capillary and positioned radially more distant from the center of the platform than the first fluid chamber and the entry port,
• wherein a capillary junction is formed between each of the metering capillary and the first fluid chamber and the overflow capillary and the overflow chamber, whereby fluid placed onto the disk at the entry port flows by capillary action to the junction of the metering capillary and the first fluid chamber, and excess fluid flows by capillary action to the junction of the overflow capillary and the overflow chamber;
• and wherein rotation of the platform at a first rotation speed motivates fluid displacement in the overflow capillary into the overflow chamber but not fluid displacement in the metering capillary, whereby rotation of the platform at the first rotational speed drains the fluid from the entry port into the overflow chamber;
• and
• wherein rotation of the platform at a second rotation speed that is greater than the first rotational speed motivates fluid displacement of the volume of the fluid in the metering capillary into the first fluid chamber;
• and wherein each of the first and overflow chambers also comprise air displacement channels whereby air displaced by fluid movement is vented to the first surface of the platform.