Authors:
Hae Woon Choi
Seon Bong
Department of Mechanical and Automotive Engineering, Keimyung University, Daegu, Republic of Korea 704–701

Dave F. Farson
Laboratory for Multiscale Processing and Characterization, The Ohio State University, 1248 Arthur E Adams Dr, Columbus, Ohio 43221

Chunmeng Lu
L. James Lee
Department of Chemical and Biomolecular Engineering, The Ohio State University, 140 W 19th Ave, Columbus, Ohio 43210

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.