Micro elastofluidic liquid diode for programmable unidirectional flow control

Haotian Cha

doi:10.1039/D5LC00438A

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Micro elastofluidic liquid diode for programmable unidirectional flow control

2025-09-20

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Haotian Cha

Fariba Malekpour Galogahi

DOI：10.1039/D5LC00438A

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Abstract

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Controllable liquid transport is essential for fluid regulation in wearable biosensing platforms. Particularly; unidirectional flow offers a passive; geometry-dependent strategy to direct liquid movement without external actuation. However; most previous studies have focused solely on achieving unidirectional flow; with limited exploration of real-time tunability or reconfigurability. Here; we present a tuneable open-channel microfluidic platform featuring a chevron–ratchet geometry that enables passive and reversible liquid diode behaviour. Flow directionality and velocity are dynamically modulated through surface wettability tuning and mechanical stretching. A theoretical force model was first established to describe asymmetrical spreading; governed by Laplace pressure gradients and geometric curvature. Numerical simulations based on energy-minimization principles further elucidated wetting behaviour on structured surfaces. Concurrently; experimental validation confirmed three distinct flow regimes—pinned; unidirectional; and bidirectional—controlled by plasma-induced wettability modulation and applied mechanical strain. Stretching the channels along orthogonal axes led to programmable switching of flow states and geometry-sensitive pinning thresholds. We further integrated a hydrogel film as a sweat-acquisition interface and demonstrated sustained unidirectional transport under physiologically relevant inflow. This proof-of-concept validation complements the fundamental findings and highlights the translational potential of our open-channel platform as a simple; tuneable; and pumpless approach for wearable diagnostics; adaptive liquid routing; and flexible microfluidic circuitry.