The fabrication of air-channels for microelectromechanical systems and microfluidic devices using polynorbornene and polycarbonates as thermally or photolitically decomposable materials to form air-gaps in dielectric materials has been reported. In this study, the incompatibility of some overcoat polymers with the sacrificial materials was addressed. SiO₂ was used as a barrier layer for the fabrication of single- and multi-layer air-channels via different sacrificial and overcoat materials. The structural rigidity of SiO₂ mitigates problems associated with overcoat polymers that can easily deform at the processing temperature (overcoat cure or sacrificial decomposition temperature). The chemical inertness and low permeability of SiO₂ allows the use of solvent-cast polymers, for which the solvents would have otherwise dissolved the sacrificial material.