Speaker
Description
We use theory and experiment to elucidate how acoustic and ultrasonic waves drive fluid flow and mass advection in porous media. This work provides insight into acoustically induced transport relevant to subsurface fluid motion during seismic events and establishes a framework for integrating acoustic actuation into point-of-care diagnostic platforms.
Experimentally, we demonstrate acoustic-driven transport in porous nitrocellulose paper used for lateral flow immunoassays by employing a floating electrode unidirectional transducer to generate a directional Rayleigh wave in a lithium niobate substrate. The Rayleigh wave couples into the porous medium by leaking an ultrasonic field, which generates a steady flow that significantly accelerates the propagation of a colorimetric reaction front in a model chemical system compared with passive capillary transport. Systematic variation of excitation and substrate parameters identifies operating regimes that enhance transport while maintaining minimal thermal effects, which is essential for sensitive biochemical assays.
We desing our experiments such that the ultrasonic wavelength is large compared with the pore size, which is appropriate for many fibrous and paper-based materials. In this limit, the induced transport appears as a net drift of fluid mass along the direction of acoustic propagation. To interpret these observations, we develop a theoretical description of acoustically driven flow in porous media based on an ensemble of cylindrical pores with randomly distributed orientations. By computing the streaming-induced flow within individual pores and averaging over orientations, we obtain an effective Darcy-type description of the net transport that incorporates both pore geometry and acoustic forcing.
By linking experimental observations with a physically grounded theoretical model, this work identifies the mechanisms governing acoustic streaming in porous substrates and demonstrates the feasibility of using Rayleigh-wave-based actuation to actively control fluid and chemical transport in porous media. These results open new opportunities for acoustically enhanced porous microfluidics and rapid, tunable transport in diagnostic and analytical systems.
| Country | Israel |
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