Studies on Gas Flow through Smooth Microchannel Surface – Fabrication, Characterization, Analysis, and Tangential Momentum Accommodation Coefficient Comparison

Abstract

In the present work, experimental and numerical findings of tangential momentum accommodation coefficient (TMAC) on smooth microchannel surface and comparison with rough surface was performed. A modified silicon micromachining technique was used to achieve smooth surface of the microchannel. About two orders of magnitude decrease in surface roughness was obtained when compared to previous studies. Second order slip model was derived, and a special procedure was developed to simulate the gas flow in microchannel from slip-to-transition regimes. The microchannel system with 20 parallel channels were fabricated on a surface modified silicon surface and flow characteristics were studied by generating accurate and high resolution experimental data with comparison of simulation results. TMAC values were found up to an outlet Knudsen number of 0.851 with nitrogen and the second order slip coefficients were found. When compared to previous TMAC values for rough surfaces, low values were obtained in the present case. This decrease is an indication of the increase in slip velocity due to the reduction of surface roughness.