A method is provided herein, the method includes: applying a sample comprising target nucleic acids to a sample application zone of a substrate; and flowing a nucleic acid amplification reaction mixture across a length of the substrate through the sample application zone to amplify the target nucleic acid forming a nucleic acid amplification product; wherein the target nucleic acid having a first molecular weight is substantially immobilized at the sample application zone and wherein the amplification product having a second molecular weight migrates away from the sample application zone. An associated device is also provided.