Expandable microspheres for the handling of liquids.

Two novel concepts for controlled handling of liquids in microfluidic systems are presented: a one-shot micropump and a normally open one-shot valve based on thermo-expanding Expancel microspheres. Expancel microspheres are small spherical plastic particles that, when heated, increase their volume considerably. We show that liquid volumes in the nanoliter range can be actuated against a counter pressure of at least 100 kPa and fluid flow can be inhibited in a microchannel against pressures of at least 100 kPa.