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]