Mass flow and tangential momentum accommodation in silicon micromachined channels

High-precision experimental results are reported showing the tangential mom entum accommodation coefficient (TMAC) for several gases in contact with si ngle-crystal silicon to be less than unity. A precise and robust experiment al platform is demonstrated for measurement of mass flows through silicon m icromachined channels due to an imposed pressure gradient. Analytic express ions for isothermal Maxwellian slip flows through long channels are used to determine the TMAC at a variety of Knudsen numbers. Results from experimen ts using nitrogen, argon and carbon dioxide are presented. For all three ga ses the TMAC is found to be lower than one, ranging from 0.75 to 0.85.