Standardized Metrics for Polydimethylsiloxane Bonding: Rupture Pressure–Stress Correlation in Air Plasma-Activated Interfaces

Reliable and robust bonding of PDMS interfaces is essential for performing microfluidic and flexible electronic devices, where surface activation governs interfacial bonding. This study introduces a geometry-correlated scaling function that converts rupture pressure into maximum von Mises stress at the bonding interface, a threshold as a material property for a given interface, enabling a standardized cross-platform evaluation of bonding strength. Using this material threshold-based framework, we assess the efficacy of air plasma treatment through hydrophilicity measurements, adhesion testing, rupture experiments, and thermal postbonding treatment. Postbonding incubation enables interfacial stresses of 60–120 psi (414–827 kPa), comparable to the published results of oxygen plasma bonding. The strain energy release rate (SERR) of 0.02–0.07 in-lbf/in2 (3.5–12.3 J/m2), while below typical fracture energies, is consistent with the nonasymptotic nature of the rupture configuration. Aging studies show that mild air plasma exposure supports stable long-term bonding. These results show air plasma as a feasible alternative to oxygen plasma and provide a transferable protocol for consistent, interfacial rupture stress-based evaluation of the interfacial bonding performance across platforms.