A simple and low-cost approach was proposed for prototyping PDMS based microfluidic devices by transferring adhesive film microstructures onto a flexible substrate as a mould for PDMS replicas. The microstructures were engraved on an adhesive coated film using a commercial cutting plotter and then transferred (or laminated) onto a flexible substrate, allowing for engraved isolated patterns. The proposed technique was demonstrated by a hydrodynamic focusing microfluidic device, having splitting and re-combining sheath channels. The whole processing could be finished within 1 h in a normal laboratory environment. This approach offers an easy, flexible and rapid prototyping of microfluidic and lab-on-a-chip devices to users without expertise in microfabrication. In addition, by minimizing the use of chemicals, the process becomes more environmentally friendly than conventional photolithography based micro-fabrication techniques.