GASEOUS SLIP-FLOW IN LONG MICROCHANNELS

An analytic and experimental investigation into gaseous flow with slig ht rarefaction through long microchannels is undertaken. A two dimensi onal (2-D) analysis of the Navier-Stokes equations with a first-order slip-velocity boundary condition demonstrates that both compressibilit y and rarefied effects are present in long microchannels. By undertaki ng a perturbation expansion in epsilon, the height-to-length ratio of the channel, and using the ideal gas equation of state, it is shown th at the zeroth-order analytic solution for the streamwise mass flow cor responds well with the experimental results. Also, the effect of slip upon the pressure distribution is derived, and it is obtained that thi s slip velocity leads directly to a wad-normal migration of mass. The fabrication of wafer-bonded microchannels that possess well-controlled surface structure is described, and a means for accurately measuring the mass flow through the channels is presented. Experimental results obtained with this mass-how measurement technique for streamwise heliu m mass how through microchannels 52.25-mu m wide, 1.33-mu m deep, and 7500-mu m long for a pressure range of 1.6-4.2 atmospheres (outlet pre ssures at atmospheric) are presented and shown to compare favorably wi th the analysis. [147]