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the ture lecu rane is of structures based on this membrane material provide a typical gas flow rate of 0.93 sccm/cm in the wide r MCE) y inert licatio perature gradient, within which the gas flow is constrained to the free molecular or transitional gas flow regimes (Fig. 1) [3,4]. For transpiration to be significant, it is necessary for the hydraulic diameter, d, to be smaller than the mean free path, k, of the gas molecules, i.e., the Knudsen number, Kn(k/d), must be greater than unity. For two large chambers connected by nanochannels that are located within a thermal transpiration element, as in Fig. 1, the ra-pore-density, and high thermal conduction are challenges, along with a potential for a relatively high density of structural defects that allow leakage and reverse flow. The contribution of MCE membranes toward improving micro-scale Knudsen pumps can have significant applications. Most of the micro-scale pumps reported to date are relatively expensive to manufacture because of multi-mask lithographic fabrication [13– 17]. Extended reliability also remains unproven for pumps that re-quire micro-scale moving parts. As a consequence, gas sensing and analysis use meso-scale or macro-scale gas pumps [18–20]. Pro