Led-based multibeam photoacoustics combined with electrical circuit-based modeling for the analysis of multispecies mass transport through thin membranes

This work develops photoacoustic-based experimental methods for comprehensive characterization of multispecies mass transport from donor compartments to thin-membrane acceptor systems in perfect contact, supported by dedicated mass transfer modeling framework. Multibeam configurations are implemented in photoacoustic setups operating in front-side detection and diffuse-reflection geometries. The setups are calibrated and adjusted prior to measurements by means of transmission-mode photoacoustic experiments conducted under steady-state conditions. Finally, the methodologies were applied to a model system undergoing photoinduced decay, enabling characterization of bulk transport kinetics as well as interfacial equilibration monitored through time-dependent changes in interfacial reflectivity. For the analysis of bulk transport data, a lumped electrical-circuit (EC) model is introduced. The model is formulated in tableau form, linking species population dynamics to an interaction matrix representing mass-transport couplings consistent with the underlying diffusion–reaction framework. A simplified approximation of the model is further proposed and validated against experimental results. The combined experimental–modeling framework provides an effective approach for quantitative analysis of coupled diffusion, reaction, and interfacial processes in thin-membrane systems.