Leak Testing and Seal Qualification of Vat-Printed Fluidic Components: Through-Defects, Interfaces, Pressure Decay and Bulk-Permeation Boundaries

Vat photopolymerisation can fabricate monolithic microfluidic channels, integrated covers, valves, connectors and complex flow paths, but fluidic success cannot be inferred from printability or dimensional accuracy alone. Published SLA and DLP studies report pressure-driven flow, pressure-to-failure tests, leak-free bonded interfaces, reusable connector burst-pressure measurements and, in a recent hydraulic-fitting comparison, failure of printed components to achieve application-level leak tightness despite acceptable dimensional tolerances. This Engineering Review establishes a state-based qualification framework for leak testing and sealing of vat-printed photopolymers. It distinguishes molecular permeation through the bulk network from through-defect, crack, interface, connector and seal leakage; separates proof, leak-rate and burst tests; and requires reporting of pressure differential, medium, temperature, hold time, trapped volume, compliance, connection hardware and failure location. ASTM E2930-26 is identified as a current pressure-decay method anchor for rigid vessels, while ISO 20484:2017 and ISO 20485:2017 provide leak-testing vocabulary and tracer-gas method context. 3Dresyns microfluidic materials, its Microfluidics IFU and the Self-Heal Seal additive family are included only as manufacturer implementation examples. No leak rate, pressure rating, self-sealing efficiency or service life is inferred from product positioning.