a method and system are disclosed for manipulating the flow of gases into and out of a microfluidic circuit to regulate pressure within the circuit or to provide for the delivery of gases to or removal of gases from the circuit . pressure within the microfluidic circuit may be increased or decreased to modify physical or chemical properties of fluid within the circuit , or to modify reaction kinetics . gaseous reactants may be added to the circuit , and reaction products or excess reactant gases may be removed the circuit according to the invention . warm or cool air or other gas may be flowed over liquid reactants within the circuit to perform a warming or cooling function . various biochemical reactions or processes , including for example polymerase chain reaction and ligand - receptor binding , may be performed with the use of the inventive method and system .