A new, rapid, environmentally friendly prototyping method is presented. This method is based on the use of a negative, water-developable dry-film photoresist as the structural material. In this method, the photomask is prepared by printing microchannel patterns to either a sheet of Vellum paper or a transparency by an office laser printer. It follows by transferring the patterns to the dry-film photoresist by low-dose UV exposure. The patterned photoresist is developed by spraying with pressurized warm water, which makes this method unique and environmentally friendly. The developed SR-3000 with engraved open patterns can be sealed, after plasma-oxidation, to poly(dimethylsiloxane) (PDMS) with a good strength of bonding as high as the 340–410 KPa (50–60 psi) range, strong enough to hold pressure for typical microfluidic applications. The turn-around can be accomplished in 3 h with no cleanroom facility. Microchannel designs were prototyped to demonstrate three typical applications in microfluidics.