Femtosecond laser micromachining and application of hot embossing molds for microfluid device fabrication

Femtosecond laser micromachining was used to create microfluid channel patterns on AISI 304L stainless steel to fabricate hot embossing mold patterns. To characterize the machining process, measurements of single pulse ablation spots with pulse energies from 13 to 500 nJ were used to determine ablation threshold as 0.19 J/cm2. The volume of material removed per pulse increased steadily with pulse energy but ablation efficiency relative to the evaporation enthalpy of removed material had its maximum value of 2% at 65 nJ. Molds with fluid channel features 12 μm deep and as narrow as 8 μm wide could be machined by laser ablation. A mold with channels 75 μm wide and 10 μm deep was machined and used to emboss a microfluidic micromolecular magnetic separator pattern in polymethyl macryolate polymer.