Turning Porous Functional Materials into Directional Transport Platforms with Unidirectional Surface Acoustic Waves

ABSTRACT Porous media enable absorption, filtration, separation, and high‐area interfacial transport in chemical and diagnostic systems, but sustained directional flow remains difficult because tortuous pores and acoustic losses promote bypassing, weak flow, and counterflow. Here, we show that floating‐electrode unidirectional transducers (FEUDTs) convert porous materials into actively pumped transport platforms by generating predominantly unidirectional surface acoustic waves (SAWs) that couple more effectively than conventional interdigital transducers across wet multilayer interfaces. Across variations in pore size, permeability, sample thickness, and fluid viscosity, transport is strongly enhanced when the SAW wavelength is comparable to the characteristic pore dimension, establishing a practical design rule. Under these conditions, FEUDTs drive directional flow up to 0.6 mm at sub‐watt power, about 600 times faster than diffusion alone. They also sustain pumping in prewetted porous media, where capillary effects are removed, producing velocities above capillary‐driven flow under matched conditions and far above thermally induced transport. A reduced theoretical framework captures the main trends and identifies transducer architecture, pore geometry, and actuation strength as key parameters for tunable, long‐range transport in porous functional materials, including dermal tissue.