We have fabricated a low-cost disposable polymerase chain reaction thermal chamber that uses buoyancy forces to move the sample solution between the different temperatures necessary for amplification. Three-dimensional, unsteady finite element modeling and a simpler 1-D steady-state model are used together with digital particle image velocimetry data to characterize the flow within the device. Biological samples have been amplified using this novel thermal chamber. Time for amplification is less than 30 min. More importantly, an analysis of the energy consumption shows significant improvements over current technology.