This work introduces X-fenes, a unifying framework in which all two-dimensional crystals—graphene, silicene, phosphorene, h-BN, borophene and transition-metal dichalcogenides—are interpreted as confinement cavities for a longitudinal vacuum mode described by the Ψ-field.Within this picture, each monolayer defines a characteristic Ψ-resonance frequency, a BKT-like coherence scale, a screening length, and a lattice-topology factor that together determine its electrical, thermal and optical response. The study derives universal Ψ-scaling laws linking measurable quantities—joint electrical–thermal resonance frequency, resonance amplitude ratio, and strain–absorbance coefficient—to the underlying vacuum parameters of any X-fene.This allows two-dimensional materials to be treated as vacuum-wave circuit elements with well-defined Ψ-impedance and conversion channels. A complete and falsifiable experimental programme is proposed using THz spectroscopy, strain-tunable optics, and 2D heterostructure transport.If validated, X-fenes would provide the first laboratory-accessible platform for engineering longitudinal vacuum modes using existing 2D materials technology.