Abstract: A modular cassette is provided for separating a composite fluid into at least two component parts thereof during centrifugation. The modular cassette includes: a housing defining a fluid inlet, a fluid outlet, and a chamber for fluid separation; a fluidic channel configured to provide fluid communication between at least two components of the modular cassette; a heat expanding valve including: a flow pathway including undulations configured to facilitate closing of the fluidic channel, wherein the heat expanding valve occludes one or more of the undulations of the flow pathway to close the fluidic channel; and a heating element configured to actuate the heat expanding valve.