With the major advances in soft lithography and polymer materials, use of microfluidic devices has attracted tremendous attention recently. A simple and fast micromachining process is highly in demand to prototype such a device efficiently and economically. In this paper, we first reported an out-of-cleanroom printing-based integrated microfabrication process, referred to as the lab-on-a-print (LOP), for rapid-prototyping three-dimensional microfluidics. Using this lab-on-a-print process, we demonstrated the potential to accomplish an entire design-to-fabrication cycle within an hour, including about 70 microm resolution of direct-lithography patterning, well-controlled polyimide wet etching, three-dimensional pattern alignment and multilayer wax thermal-fusion packaging. A microfluidic gradient generator was prepared and tested for validation of the lab-on-a-print microfabrication process.