Abstract: A reactor and methods of use are disclosed for amplification of an amplicon. The reactor includes a housing having a fluid path with a fluid inlet and a fluid outlet and one or more reaction chambers suitable for housing the amplicon. The reaction chambers are positioned within the housing in thermal communication with a fluid flowing in the fluid path to heat and/or cool the reaction chambers and the inside of the reaction chambers are coated with or are a plastic material. A variable temperature fluid source is in fluid communication with the fluid inlet and the fluid source is configured to provide fluid at temperatures suitable for amplification, including a denature temperature, an anneal temperature, and an extension temperature. A controller is coupled to the variable temperature fluid source to control a fluid temperature within the fluid path by controlling the variable temperature fluid source.