Comparison of roughness parameters for various microchannel surfaces in single-phase flow applications

Recently, a set of new roughness parameters was proposed by Kandlikar et al. and Taylor et al. for reporting surface roughness as related to fluid flow. The average roughness R-a parameter is often used in microfluidic applications, but this parameter alone is insufficient for describing surface roughness; a specimen with deep grooves and sharp obstructions can share the same average roughness value as a relatively smooth surface with low uniform surface roughness. Because the average roughness parameter is broad, it is difficult to assess the surface topography features that result from different machining processes or etches. A profilometer and a digital microscope are used to examine the surface roughness profiles of various materials submitted to different machining techniques. The materials studied will be similar to those used for microchannels including aluminum, stainless steel, copper, and silicon. Depending on the material, these samples are submitted to several machining processes, including milling, grinding, fly cutting, and microfabrication techniques. These machining processes and microfabrication techniques are of practical interest in microfluidics applications. After studying the surface roughness patterns exhibited in these samples, the roughness parameters employed in some of the recent roughness models are evaluated. This study is expected to provide more understanding of assorted surface roughness.