Provided herein is a method of making, comprising transporting reagents to a reactor in a microfluidic path device, wherein the reagents include a synthetic gene of interest, a polymerase, a buffer, a first primer having a first region specific to the synthetic gene of interest, and a second primer, wherein the second primer comprises a poly-T sequence of ≥150 base pairs (bp) or a poly-A sequence of ≥150 bp and a second region specific to the synthetic gene of interest; controlling a temperature of the first reactor to perform a polymerase chain reaction within the microfluidic path device to amplify the synthetic gene of interest using the first primer and the second primer to form a synthetic product including the poly-A sequence of ≥150 bp; and transporting the synthetic product out of the first reactor, wherein the synthetic product comprises a synthetic DNA template for in vitro transcription.